Maintenance 1938 style

[a10 gf]

Project well under way, a scan\ocr of the contents of an old book I enjoy reading now and then, got lot's of great\funny\useful tips & tricks from a bygone era, much of it still very actual.

Very probably no copyright anymore, & used for informational\recreational purpose only.

Look for "Chapter xxx" in posts below.

[muskrat]

Good one e, I'll be watching for it. I love reading about old bike stuff.
Cheers

[a10 gf]

CHAPTER XIX , RIDING KIT

How to Choose It
447.  Riding kit is a matter depending upon personal preference, the type of work indulged in, and the depth of one's pocket. The notes that follow therefore point out the respective advantages of the various types of garments and give hints and tips whereby a rider, even in the worst of weather, should have no difficulty in keeping dry and reasonably warm.

Trench-Coats
448. Many types of outer garments are available. The most popular with the average rider is undoubtedly the multilayer type of trench coat that is made specially for motor cycling. These, with their fleecy lining (which can be detached in hot weather), are warm and are so cut that it is almost impossible for water to find its way in. One great advantage which they possess is that they are not unsightly, and therefore can be worn "about town" when the machine is parked.
Various qualities are available, and the best that can be afforded should be purchased. Whatever the decision as to quality, be sure that the coat is on the large side. If a small size is bought there may be difficulty in getting on as many under-garments as might be desirable during a cold spell; and, what is worse, the seams may give, so letting in the water. Another point, of course, is that a really large and lengthy coat can be tucked around one to protect the legs.

Leather Coats
449. Leather is excellent for keeping the wind out and ensuring warmth, but, except when specially dressed, is useless in heavy rain. This means that it should only be used as an under-garment unless the weather is "set fair ". An ordinary leather coat may, however, be rendered reasonably waterproof by an application of Ronuk or some similar polish. Specially-dressed horsehide coats are obtainable which, though they are expensive and heavy, and need redressing, say, every twelve months, will protect one from almost everything. Like trench coats, they must be double-breasted and cut on the really generous side.

Rubber Ponchos
450. In the days of long-distance trials ponchos were the experienced competition rider's usual choice. They are made of black rubber with a cloth backing and are slipped over the head. Two types of neck opening are obtainable: (1) flexible rubber, and (2) a gusseted affair with a hook and press-studs, or with a Zipp fastener. The latter is the more convenient so far as putting on and taking off the poncho is concerned, and lasts better, but the former, due to the soft rubber clinging to the neck, naturally makes the more watertight "joint ".

451. The chief objection to a poncho is, first, the difficulty of getting it on and off, and, secondly, its un- sightly barrel-like shape. For the long-distance all- weather rider, however, it is an excellent outer garment.

Competition Coats
452. A type of coat which is extremely popular is the so-called "competition" coat, which is of similar material to the poncho but fashioned on the lines of a trench coat. These are generally unlined, are therefore cheaper than the multi-layered trench coat, and, like the poncho, are used with a coat of some sort underneath. They are perhaps better than a trench coat for keeping out ultra-heavy rain, because of their rubbered seams,but they do not look so well; also contact with petrol and oil spoils the rubber proofing. As with all other coats, they should be on the large side.
For preference the collar should. have a cloth facing, since if it is of rubberized material, the black of the rubber will transfer itself to one's neck in wet weather.

Gloves
Leather Gloves
453. Gauntlet gloves, except in warm weather, or unless handlebar muffs are used, are essential. These are made in any styles and at various prices. Motor cycling rather than motoring gloves should be purchased; in other words, avoid buying soft gloves which will both soak up water and tear. Horsehide is about as good as anything, and if it is dressed so as to be more or less rain-proof (see Paragraph 449), so much the better. Actually, no leather gloves will keep out the rain indefinitely, but, like beers, some are better than others.

454. Gloves should be bought amply large enough, since to have them tight is to spell numb fingers in cold weather due, among other things, to their restricting the circulation. If funds will permit it is a good scheme to have a large, thick, woolly-lined pair for winter riding, and an unlined smaller pair for summer work. Thick, stiff gloves mean poor control of one's machine, so it is undesirable to wear a heavy pair except when they are necessary from the warmth point of view.

455. Many riders of machines with twist-grip controls favour mitt-type gloves for very cold weather; these, . although cumbersome, are much warmer than gloves with separate fingers.

456. Leather gloves, as mentioned above, will not keep the rain out indefinitely. There are, however, specially made rubber gloves on the market, which, while not particularly warm and apt to become clammy in use, do keep the hands dry. These have reinforced seams and are admirable, but naturally do not last for ever. There are also excellent single-finger gloves made from proofed fabric, which can be obtained either for ordinary wear or for wear over leather gauntlets.

457. A good tip for use with ordinary gloves is to sew a square of wash leather to the back of one of them for wiping rain off the goggles.

Silk Under-Gloves
458. Since if only a rider can keep his extremities warm, he is himself warm, there is much to be said for slipping a pair of thin silk gloves beneath one's ordinary gloves in very cold weather. There is nothing to touch silk for this purpose.

Handlebar Muffs
459. For very cold or very wet weather handlebar muffs, although clumsy and somewhat unsightly, are a boon and a blessing. A substitute that has sometimes been used by competitors in long-distance events, when bad weather has found them without muffs, consists simply of thick newspaper tied round the end of each bar in the form of a cone and thickly anointed on the outside with oil to make it waterproof.

Protecting the Legs
460. For all-weather riding on a machine not equipped with legshields, waders, Wellingtons, or some similar articles of apparel are almost essential. Here the tip is to get a pair that is large enough to accommodate the largest pair of boots ever likely to be worn, yet not so big that all sense of control is lost, for one foot will be wanted for braking and the other, perhaps, for operating the gear change-operations which both require a certain amount of delicacy.

461. Many riders attach the straps on waders to their trouser buttons. A better scheme, however, is either to fix them to a small strap encircling one's waist, or to attach a tape to the straps and loop this tape over one's shoulders. As a result the early loss of trouser buttons will be prevented if nothing else! Straps round the ankles, or even rubber bands cut from an old car-size inner tube, will facilitate walking in the waders, but if the waders are made too tight round the ankles the circulation will, of course, be affected.

462. Riding boots look smart in fine weather, though hardly after a muddy run. They also have the objection that they do not protect the knees. Nevertheless they are much used by competition riders, largely because they lack the clumsiness of waders.

463. For the man who is not out in all weathers, and only needs cover for his legs on the occasions that he is caught by a shower, there are many excellent examples of mackintosh leggings. These are cheap, and if of good quality, last for two or even three years without perishing. They are useful, too, as a protection against splashes from passing vehicles for riders who rely on legshields as their first line of defence against the elements.

464. Undoubtedly the most difficult parts of the body to keep dry in very bad weather are the thighs. Rain drives along the top of the tank-often with most uncomfortable consequences. A poncho, if carefully arranged at the start of the run, will give perfect protection, but an equally effective precaution which certainly causes less trouble is a pair of waterproof shorts; these can be obtained in various forms from firms specializing in clothing. There are also excellent "tummi-pads" obtainable for use with trench coats. (See also Paragraph 446.)

Headgear
Berets
460. Widely differing views are held on the question of the best type of headgear. Some riders prefer berets, others ski-caps, others leather helmets, and still others ordinary cloth caps. Berets have the great advantage that they don't blow off, but they are useless when their wearers are faced either with blazing head lamps or the setting sun, or when rain is driving into the eyes; that is, unless they are used in conjunction With a so-called tennis peak, or goggles which have the upper half of the lenses tinted.

Ski-caps
466. Many hard riders maintain that for all-round use there is nothing to equal a well-fitting ski-cap, which has a peak properly sewn in; but the peak must be large if it is to be effective, and it must be stiff or the user will find his vision at high speed suddenly blanked off. Whether the ski-cap has the fal-lals or not is a matter of personal preference, but certainly very few motor cyclists whom one encounters on the road ever have the ear flaps in use.

Cloth Caps
467. Ordinary cloth caps, so long as they fit well and have a large, waterproof peak are good, but they seldom stay on quite so well at speed as does a good ski-cap.

Helmets
468. Lastly there is the flying helmet, which is certainly delightfully cosy when the temperature is around freezing point. Helmets do, however, tend to make the wearer drowsy after many hours in the saddle, and when a fur lining is used the fur invariably picks up a lot of dirt which sooner or later is transferred to one's face and neck.

Goggles
469. The number of different types of goggles available is legion, but whatever happens no motor cyclist should dream of purchasing a pair with lenses of ordinary glass. Either safety-glass or non-flam celluloid goggles should be bought, preferably with the widest possible vision.

470. One of the most popular types of safety-glass goggle is the R.A.F. type face mask, which, if well made, will keep all the wind and every speck of dust out of the eyes. They are not pretty and the fur becomes dirty in time, but certainly they are some of the finest goggles for motor cycling that are obtainable.

471. Whether goggles with separate eye-pieces will fit properly depends upon the contour of one's face. Avoid, however, goggles which, to be windproof, have to have the elastic very tight.

472. The best goggles of all are those often worn by racing car drivers, and are worthy of mention merely because they are the best; but they cost a good deal more than most motor cyclists will feel inclined to pay. These have separate eye-pieces lined with soft rubber, and should prove absolutely windproof and watertight. They are available in two grades, the better of which has curved lenses.

473. Safety glass is available either tinted or plain. Tinted glass is restful to the eyes, and after the goggles have been on a few minutes the tint only makes the countryside look dull without affecting its colouring. Most riders, however, dislike them for night work, as they find that they cannot see through them so clearly as with plain safety glass.

474. Far cheaper than safety-glass goggles are those made of celluloid. Many motor cyclists prefer the one- piece type of celluloid goggle to all others, for they are light, cool, give the widest possible vision, and only cost about a shilling. When they become badly scratched through carelessness-well, another pair is bought. The flimsy type, however, should be given a miss, since wind pressure will press them on to the eyelashes, if any fast motoring is indulged in, with disconcerting results; there will also be trouble with them in wet weather. Two features of these goggles are that they have little tendency to mist and in wet weather raindrops tend to be blown off the curved surface.

475. Another useful little tip is to stitch the elastic to the cloth edging before the goggles are put into use; this Will prevent the likelihood of the elastic breaking away long before the useful life of the celluloid is past.

476. Many riders complain that they cannot wear goggles in wet weather. Except for those who are cursed with glasses there should be no trouble with a pair of one-piece celluloid goggles even in the worst of weather (barring snow!). If they steam on being put on, run a finger over the inside. For the outside surface, use one of the special preparations if trouble is experienced, or even the juice of a potato or an apple which after application should be dried off in front of a fire.

477. It is well worth while taking a little care with one's goggles. Always breathe on them before wiping them and always use a silk handkerchief for cleaning purposes, not a linen or cotton rag. If possible go one better and wash the goggles.

478. Another form of eye shield is the visor or face screen, which is particularly suitable for use in wet weather since the rain does not collect on its curved surface. In addition, a visor protects the lower part of the face from stinging rain or snow. Sidecar passengers, at all events if the screen is of small dimensions, are likely to find a visor admirable.

General
Keeping Warm in Very Cold Weather
479. It is an axiom-as has been mentioned already- that if one's hands and feet are warm one's whole body is warm. Therefore these members should receive their full measure of protection. For long rides in icy weather some people wear anklets, while others use two pairs of stockings (see Paragraph 458). These schemes are good, but be wary of restricting the circulation by having stockings, gloves, or shoes too tight.

480. As regards underclothes, silk or wool should be worn next to the skin; silk is best. A pullover or, even better, a golf jacket or polo jumper, are useful articles of apparel. Leg-shields and handlebar muffs, of course, help enormously. Whether these are fitted or not, take care that your outer garments are so arranged that n9 air flowing along the tank can strike upward underneath the outer layers.

481. Newspaper makes a very effective breast-plate if folded and arranged beneath one's coat or waistcoat. (See also Paragraph 459.)

482. A rug wrapped round the legs of the sidecar passenger in the form of a cone will go a long way to ensure the comfort of the occupant of the chair. He -or more probably "she "- in icy weather will feel the cold quite as much as the driver, who at least has the job of controlling the machine to occupy his mind; and far more care should be lavished on his (or her) comfort than is usually the case.

483. Hot-water bottles are not an unreasonable request, nor the suggestion that the hood should be raised. Perhaps even better than a hot-water bottle is a large baked-in-its-jacket potato, a homely artifice for keeping hands warm which was well known to our forefathers.

484. While on this topic of keeping warm mention must be made of hot cocoa which is as good a drink as one can possibly have on a long run. A cheap vacuum flask will keep it hot for hours; better still-if on a long run-take two small flasks so that the second drink shall be really hot.

Scarves
485. If funds will run to it, there is nothing to beat an angora-wool scarf for softness, warmth and general comfort. However, any good wool scarf will serve. but it should be long enough to encircle the neck twice and still reach the waist. Many riders arrange their scarves so that one end runs right down the front and passes between their legs; in this way it prevents wind and cold finding their way past the openings in the coat and trousers.

486. A small towel as an under-scarf is excellent ill dirty weather. Another dodge frequently adopted by riders who must appear smart and clean at the end of their journey is to use a silk square tucked in and around their collars under their ordinary wool scarf.

Repairing Torn Waders
487. Generally a wader or poncho is tom or gashed long before the rubber material of which it is made has perished. Do not throw it away, but obtain some of that very excellent black sheet-rubber which is sold both in tyre-repair outfits and separately. Wash the rubber around the tear with petrol, scratch it well with sandpaper or a piece of file-card, apply a thin film of the special rubber solution, and, when this solution is really tacky, press home a piece of the patching rubber, previously cut to shape. In other words, treat the wader or poncho as if it were an inner tube. By the way, do not use a piece of old inner tube instead of the patching rubber, since it will not stick on nearly so well, nor look so neat.

488. Where the garment to be treated is made of ordinary mackintosh, this method will not always apply. However, "Mend-a-Tear ", obtainable from cycle shops, leather shops, etc.. will do the trick.

[a10 gf]

CHAPTER X: ENGINE I

Horse-power Rating
203. There are two forms of h.p. rating still in use: One is the arbitrary rating by which an engine of 250 c.c. is a 21 h.p. engine, an engine of 350 c.c. is a 21 h.p., and an engine of 500 C.c. is a 31 h.p. This rating was introduced in the early days of motor cycling, but owing to the great increase in power output a new form of rating, called the A.C.U. rating, was introduced a few years ago. The latter assumes that each 100 C.c. of, engine capacity is equivalent to I horse power. By this rating a 350 cc engine is 3.50 h.p. At the present time the maximum output of most engines is, of course, considerably greater than either the nominal rating or even the A.C.U. rating.

Decarbonizing
204. It is advisable to decarbonize an engine at fairly frequent intervals. While a low compression side-valve engine will naturally run longer without attention than a high-compression o.h.v. unit, in neither case should excessive carbon deposits be allowed to form. The reason for this is that particles of carbon are liable to become detached and cause scoring of the cylinder walls, or may get under the exhaust valve, and, by preventing it seating correctly, cause the face and seat of the valve to burn. Pre-ignition is also liable to occur owing to particles of the carbon becoming incandescent.

205. A useful tool for scraping carbon from a cylinder head and valve ports can be made from an old screwdriver. Heat up the end in a fire; and hammer the edge over into a slight curve. An old bearing scraper can also be utilized .for this purpose, or, better still, sets of special tools can be purchased from the various accessory firms. An old' pocket knife will also be found useful. When the carbon is being scraped off, care should be taken that the valve seats are not damaged, nor the cylinder bore scratched. It is generally considered best not to remove the ring of carbon at the top of the cylinder barrel.

206. When removing carbon from the crown of an alloy piston the chief point is to avoid removing metal as well. If the piston has a flat top, a flat instrument shaped like a wood chisel will do the work well, and it need not necessarily have a cutting edge. The piston should be placed upon the bench, the hands cupped round it to hold it firm, the thumbs meanwhile pressing on the instrument; this must be kept absolutely flush with the crown, and may be urged forward with the body. Often, by this method, the carbon will flake off, leaving the piston top bright and unscathed.

207. With a domed piston the work is not so easy, and it is a good plan to try an implement of copper, or -even a stout stick of solder; if these mediums will remove the carbon, the operator may scrape with impunity, as they are about as soft as the piston, and will not damage it. Sometimes the carbon will flake off if the piston crown is lightly tapped all over.

208. After the carbon has been removed, the piston crown should be polished, first very lightly with fine "blue back" emery cloth (" F. F." is the right grade, obtainable from ironmongers or oil stores) to remove any scratches or scars, and then with liquid metal polish. When using the latter, it is a good plan to lay a wad of cloth on the bench, apply plenty of metal polish, and then turn the piston crown upon it, pressing fairly hard and using an action similar to that of grinding.in valves. Care should be taken to polish the crown only, and not. to damage the top land.

Removing Carbon with Caustic Soda
209. Caustic soda solution (3,lb. to I gallon of water) is excellent for decarbonizing parts made of cast-iron or steel, but must not be used for aluminium. Leave the parts in the solution overnight, or, if in a hurry, use the solution hot, and finally wash the parts in plenty of running water. Care should be taken when caustic soda is used for decarbonization purposes that none of it is splashed into the eyes.

Polishing Engine Parts
210. Polishing the cylinder head and piston crown is well worth while. Not only will the possibility of pre-ignition through roughness in the casting be avoided, but the smoother the surface obtained the easier will be the task of removing the carbon next time. A little hard work with emery cloth (not paper), and, finally, very fine "blue-back ", will achieve the desired effect in the case of the cylinder head. See also Paragraph 208.

211. Emery cloth should never be used to polish the bearing surfaces of a piston or other sliding part if the component is of a soft met,al such as aluminium'; fine particles of the abrasive may become embedded in the surface of the metal, which will then act as a lap.

212. A lathe can often be put to good use outside its legitimate function. For instance, it can be successfully used to scour carbon from an S.v. cylinder head, particularly if the head be of the non-detachable type. Obtain a metal rod of suitable length, and fix to one end, with the aid of nuts or by riveting, a circular plate of a diameter rather smaller than the cylinder bore, then attach to the plate an ordinary pot-scourer, obtainable for a few pence; this can be accomplished most conveniently by drilling the plate and wiring the scourer to it. Fix the other end of the rod in the lathe chuck, start up, and bring the interior of the head into contact with the revolving scrubber. Be very careful not to damage the bore of the cylinder. By this method a very clean and well-polished head can be obtained, particularly if it is of the domed variety. See also Paragraph 686.
 
The "Diabolo " Method
213. A very high polish on a spindle or a valve stem can be accomplished by what is known as the "Diabolo " method. Mount the spindle or shaft rigidly in the vice, using, of course, vice-clams to prevent the jaws causing damage; coil a strip of blue-back or other very fine emery cloth round the shaft (it should be sufficiently long to enwrap the shaft about twice), and overwrap this strip with a piece of half-inch cotton tape four or five feet long. This tape should be wrapped round the emery cloth for three or four turns, leaving the two' ends 6f the tape free: By pulling alternately on the two ends on,e automatically spins the emery at high speed, at the same time exerting an even pressure. If the tapes are worked steadily from end to end along the shaft, a really excellent result will be obtained.

Crank Case Polishing
214. When polishing such parts as the crank case or gear box casing, tack a strip of medium grade emery cloth on to a strip of wood. This saves one's fingers ~d greatly simplifies the polishing of the flat portion. For curves and bends, a piece of wood shaped like a half- round file' should be used, and for inaccessible spots close to flanges and such protuberances a small pencil-like strip of wood, or, better still, an ordinary wire pan-brush will be found useful.

Compression
215. After an overhaul it is not unusual to find that there is very little compression. This is nothing to worry about, unless the trouble persists, since the oil film on the cylinder walls will probably not be perfect till the engine has run, though the piston and cylinder bore should have been well smeared with oil before assembly. In any case the various working parts take some time to bed down again.
If the compression is still bad after the engine has been run for some time, the trouble may be .due to insufficient clearance between the valves and tappets, and this point should be checked carefully by means of a feeler gauge (sets giving almost any thickness in "thous." can be purchased for less than two shillings). 'The clearance to be given varies considerably according to the particular engine, and the maker's instruction book should therefore be consulted on this point. It should be remembered that the clearance must always be checked after the valves are ground in. (See also Paragraph 220.)

Testing Compression
216. If the compression is good it should be possible, in the case of the average 500 c.c. engine, to stand on the kick-starter for two or three seconds before the compression is overcome. The test must be made with the throttle open, and a steady pressure exerted on the pedal. The fact that it is possible to kick over the engine without using the exhaust lifter does not necessarily mean that the compression is poor, since with a vigorous kick, the impetus given to the flywheels may be sufficient to carry the piston over compression. An engine of small capacity can be kicked over fairly easily, even when the compression is perfect.

Compression Ratio
217. The compression ratio of an engine can quite easily be determined; it is the ratio of the volume of the cylinder when the piston is at bottom dead centre to the volume when it is at top dead centre. In order to find the ratio, a measuring flask, graduated inc.c., is necessary, or a burette such as is used in a science laboratory. The flask or burette should be filled to a definite height with paraffin. Then, with the piston at top dead centre, pour the paraffin into the combustion chamber through the plug hole.
When the combustion chamber is full, check the amount of paraffin poured in. Then, if the capacity of the engine in C.c. is known, the compression ratio can be found by adding the C.c. of the engine to the C.c. of the combustion chamber, and dividing this number by the C.c. of the combustion chamber. As an example, if the capacity of a single-cylinder engine is exactly 500 C.c. and the combustion chamber space 100 c.c., we have (500 + 100) divided by 100, which equals 6. The compression ratio of the engine is, therefore, 6 to I.

Compression Plates
218. In cases where the compression is being lowered, it is desirable to use one thick compression plate rather than a number of thin ones; the reason for this is that the thin plates will tend to bulge where they are not under direct pressure from the cylinder base nuts, and may cause the cylinder flange to crack.

219. When a compression plate at the base of the cylinder is removed, if the engine has done a considerable mileage with the plate in position, it will be necessary to lap out any ridges which will almost certainly have been formed at the limit of the travel of the piston rings.

220. Whenever compression plates are removed or replaced, the adjustment of the valve-operating mechanism must be checked.

Leaking Cylinder-head Joint
221. Should a cylinder-head joint leak, the gasket (if any) being in perfect order, the cylinder-head should be ground in on the barrel with fine valve-grinding paste. The same procedure should be followed as outlined in Paragraph 264. A semi-rotary motion should be employed, and the process continued until both cylinder and head show by bright rings on their faces that they are making perfect contact. All traces of the abrasive should be removed with petrol before the engine is reassembled. A leaky cylinder-head joint will sometimes make a loud squeaking noise. A jointing compound may be used if desired, but with a good ground joint it should not be necessary.

Pistons
222. The chief advantage of aluminium pistons, such as are fitted to modern engines, is their high conductivity of heat, which results in cool running. With the designs normally used, large clearances have to be allowed between the cylinder walls and the piston; in consequence, little or no trouble is experienced in these.days so far as gumming- up is concerned, and this, of course, makes for easy starting. On the other hand, engines with a large cylinder bore are, in consequence, prone to what is called "pistons slap " -a tapping noise, which is noticeable when the engine is cold but tends to disappear as it warms cup. Piston slap is especially apparent when the engine is accelerating in top gear from a low speed.

223. It is only possible to obtain an approximate measure of piston clearance by means of feeler gauges, since these gauges do not readily conform with the contour of the piston.. The correct method is to utilize micro-meters; an internal micrometer should be employed for the cylinder barrel, and an external micrometer for the piston.
 
224. The greatest mechanical loss in an engine is piston friction; with a new piston it is well worth while, - after the running-in, to examine its bearing surfaces for high spots-which appear as bright areas standing out in relief from the slatish-grey of the remainder-and carefully to ease any such spots with a very fine file. (See Paragraphs 414-417.)

225. Carbon or black marks on the shirt of the piston. coupled with weak compression usually denote 'that gas is blowing past the piston rings. This. may be due to excessively worn piston rings, a worn cylinder or piston, or a scored cylinder bore. Unless the cylinder is badly worn or deeply scored, probably a set of new piston rings will effect a cure, and also ensure cooler running. Scores one or two thousandths of an inch deep may be removed by lapping (see Paragraph 235), but if they are deeper than this, or the barrel has worn more than, say, 6 thous. oval in the case of an 80 mm. bore, the cylinder should be rebored and a new piston fitted.

Piston Rings
226. The performance and running costs of an engine are seriously affected by worn piston rings, and consequently it pays to replace them when they show signs of gas leakage; especially is this so with a two-stroke. Lack of compression and/or black marks on their pressure faces point to their being due for renewal.

227. An easy method of removing piston rings is to cut three narrow strips of tin and slip them one at a time under the ends of the ring that is to be removed. Slide the strips round between the ring and the piston until they are evenly spaced. The ring can then be removed by sliding it over the strips.

228. Before' new rings are fitted the grooves should have any carbon carefully scraped out with the aid of a broken piece of an old ring, the end of which should be ground to a "vee". Modem rings are so narrow that, even for racing, there is no object in lapping them in- they will bed 'down perfectly of their own accord. Each ring should be free in its groove but without any up and down play. If necessary, reduce its thickness by rubbing it round and round on a sheet of plate (as opposed to rolled) glass, using a trace of grinding paste as an abrasive or a sheet of blue-back. Only one side of the ring should be eased, rather than both.

Piston Ring Gap
229. Whenever a new ring is fitted it must be checked for gap. The most simple method of ensuring that it is inserted truly in the cylinder bore is to slip the piston in the cylinder barrel and slide the ring up the barrel until it presses the base of thee piston skirt. The gap should then be checked with a feeler gauge; usually with a new ring it will be too small, and should be enlarged with a fine file until the space recommended for the particular engine is attained, care being taken to ensure that the ends of the ring remain parallel.
It is advisable to err on the side of a large gap rather than a small one, particularly where high-speed work will be indulged in. If too small a gap is allowed, when the engine heats up the ends of the ring will butt up against one another and set up excessive friction between the pressure face and the cylinder bore. The amount of gas that slips through the series of ring gaps under working conditions, even if these gaps are several times too large, is negligible.
When, following upon the replacement of the piston rings, the engine is next dismantled for decarbonization, the gaps should be examined for a light deposit of carbon. If this is not present, the gaps should be slightly enlarged to prevent any danger of butting.

230. Piston rings should be replaced in the same grooves and the same way up as they were originally. The gap of the top ring should preferably be on the side of the cylinder opposite to that of the sparking plug; the gaps of the other rings may be arranged with their gaps equidistant from one another, but few people in these days -even racing men- consider this essential.

Inserting Piston in Cylinder
231. There is little difficulty as a rule in fitting a piston into a cylinder. However, in certain cases it may be an advantage to use a tin sleeve to compress the rings in their grooves as the piston enters the barrel. When the rings have been placed in position on the piston, the sleeve is slipped over the rings and compressed by a piece of stiff wire bound round it, with the ends of the wire twisted together with pliers. The piston is then pushed into the cylinder, the sleeve remaining outside; in this way each ring is kept compressed until it has begun to enter the barrel.

Gudgeon-Pin
232. When the piston bosses of an aluminium piston become worn they and the gudgeon-pin bush can be reamed out and an oversize pin fitted. This is assuming that there is plenty of metal; otherwise a new piston and gudgeon-pin is the only remedy.

233. There are several methods whereby the gudgeon- pin is located endwise in the piston. The device most commonly used in modem engines is the circlip, which is merely a spring ring that engages in an annular groove in the gudgeon~pin boss. These can be removed quite easily by grasping their ears-the protruding ends of the wire- with a pair bf round-nosed pliers. Care must be taken to ensure that the circlip does not spring across the garage nor fall into the crank case. It is only necessary to remove one circlip.
When circlips are not used, usually the pin is fitted with end caps of some soft metal such as an aluminium alloy, or is clamped in the small end of the connecting rod by a pinch bolt. In the former case the pin will usually push straight out, but should it prove stubborn a good plan -if the piston is of aluminium- is to expand the piston by applying a rag steeped in boiling water.

Cylinder Barrel
234. Scores in the cylinder barrel caused by the rubbing of the end pads of a fully floating gudgeon-pin are by no means unusual. Although apparent to the eye, owing to their brightness, they may quite safely be ignored since their depth is probably negligible. If the scores can be felt with the finger, make certain that the end pads are securely fixed in the gudgeon-pin and that the pin itself is not a sloppy fit in the piston. Also see that the gudgeon- pin is not binding in the cylinder owing to the end pads protruding too far, and finally check the functioning of the lubrication system.

Lapping
235. Scores may be removed by lapping provided they are not more than a couple of thousandths of an inch deep.  The cylinder should be mounted on some form of jig; if it is clamped direct in a vice, it will almost certainly be distorted. It should be easy to bolt the cylinder to a dummy plate of some kind by means of the regular bolt holes.
The implements required are an old cast-iron piston (an aluminium one will do at a pinch) of approximately the correct diameter, without rings, and a dummy connecting-rod, which can be fashioned out of a piece of wood such as a hammer-handle, with a hole close to one end to take the gudgeon-pin. The piston used in the engine should not be employed.
Smear carborundum paste on the piston and push it up and down the bore with a screwing action. Remove the piston at frequent intervals and redistribute the paste. N ever turn the piston right round while in the barrel, or circular scratches will be formed. When the bore begins to look smooth and polished again, change over to a finer grade of paste, and finish off with metal polish. Then wash the barrel out with petrol to remove any traces of abrasive.

Cylinder Wear-A Rough Check
236. To check cylinder bore wear roughly, insert a piston ring truly just inside the cylinder. The best way to do this is to remove the piston from the connecting-rod, slide it up the barrel, and fit the ring so that it presses against the base of the piston skirt, in a part of the barrel not normally traversed by the rings. Measure the gap between the two ends of the ring by means of feeler gauges.
Next push the piston ring up the cylinder until it occupies a position within the normal travel of the rings. Again check the gap between its two ends. By testing with the piston ring at various parts of the barrel it is possible to determine roughly the amount of wear that has taken place.

Measuring Cylinder Angle
237. The simplest method of measuring the angle at which the cylinders are set in relation to the crankshaft is as follows: Take a piece of paper, and, laying it against the side of the crank case, make a template corresponding with the base of each cylinder. Continue the lines formed by the two cylinder bases until they meet, and then, with a protractor, measure the angle formed -the smaller of the two angles. When you have ascertained this angle, subtract it from 180°, and you will have the angle at which the cylinders are set.

Pre-Ignition and Misfiring
238. Drying-up, that is, the engine suddenly locking solid, may be caused by pre-ignition due to incandescent carbon particles, incandescent plug points, or roughness in the combustion chamber, as well as by partial piston seizure. It usually occurs only when the machine is being driven very hard. With an engine that is about to dry up, there is generally a fussy feeling and a "woffley" noise; although these are only of a moment's duration, the wide- awake rider can usually detect them and declutch before the back wheel locks.

239. If pre-ignition is the cause the engine will be found perfectly free when kick-started; if it is the plug that is at fault, the cure will be to fit a plug,capable of standing greater heat (see Paragraph 340). It is easy, however, to confuse drying-up through pre-ignition with that caused by a partial piston seizure since the engine, during the coast to a standstill, may cool sufficiently to free the piston. Distortion, too small a clearance, or insufficient oil are the usual reasons for actual seizure. This distortion takes the form of high spots, which will probably be apparent as small bright areas standing out in relief above the slatish grey of the remainder of the aluminium piston; the cure is to ease these high spots carefully with a very fine file.

Engine Knocking (or Pinking)
240. Assuming that an engine is properly run in {see Paragraphs 414-417), knocking may be due to a patch of roughness on the cylinder head causing pre-ignition (for polishing the head see Paragraph 210), carbon deposit, or to the use of either an unsuitable sparking plug or unsuitable fuel. Any roughness on the cylinder head can be removed with the aid of emery cloth. Particular attention should be paid to the sparking plug thread at the combustion chamber end, as this may be ragged. If an engine is of the high-efficiency type, it is generally an advantage to use one of the special anti-knock petrols that are capable of withstanding a high-compression ratio, or to use a mixture of, say, 50 per cent. pure benzole and 50 per cent. No. I petrol. It should be remembered that slight pinking does not affect the power output -only the nerves!

Spitting Back
241. When spitting back from the carburetter is experienced at low speeds malke certain that there is no obstruction as regards the fuel supply, and see that the pilot jet setting, if adjustable, has not altered through vibration. Make sure that the inlet valve is free in its guide, yet not "sloppy"; should it be sticking slightly, ease its stem with emery cloth. In the case of old side-valve engines, the trouble may be due to air leaks at the valve cap washers. Another possible cause is that the plug, under compression, may be sparking internally instead of at the points. Finally, check the tappet clearances carefully when the engine is hot (see Paragraph 268). When a two-stroke develops this habit and both the carburetter and the plug are in order, the cause is generally an air leak at one of the crank-case joints (which should be remade), or at the main bearings. Any leakage can usually be detected by the presence of oil at the joint.

242. If an engine develops eight-stroking the probability is that the mixture is much too rich owing to the float chamber flooding (see Paragraphs 56-58). Very occasionally this trouble is due to the contact-breaker points failing to close properly-appearing to close, yet actually remaining separated by a minute fraction.

243. If an engine starts quite readily, but the explosions gradually become weaker and weaker until the engine fades right out, the trouble is usually due to a restriction in the fuel supply, and you should see that the air vent at the petrol filler cap, the pipe line, and the carburetter are quite clear.

[a10 gf]

Thanks. Have finally found a way of doing the scan+ocr without getting too many initial faults.

Some errors remains here and there, fixing some as I see them, but please do not post (too many comments) about errors, it's the way ocr works, gets most right, and I don't have the time to fix every detail.

Hoping you will find some good reading and maybe useful tips in there.
Thanks

[morris]

Thanks. Great read
Already learned that I should toss the helmet, and buy by a ski cap with a large peak but not to weak, or I may find myself suddenly without vision at high speed...

[a10 gf]

^^^lol++

And to clean the googles, remember to never leave home without potato juice.
For the "she" in the sidecar, bring along a baked potato to keep her fingers warm.

[a10 gf]

CHAPTER X: ENGINE II

Crank Case and Timing Case
Paper Jointing Washers
244. When reassembling an engine after an overhaul, use brown-paper washers for the crank-case, timing-case, and other joints. Home-made paper washers are quite satisfactory if carefully made. Do not tap them out by using the crank case as a cutting edge, since the aluminium may be damaged to such an extent that it will be impossible to obtain an oil-tight joint. Press the crank case -or cylinder base- hard on a piece of good brown paper (or cartridge paper) laid flat on a table, and run a pencil round the outside of the case. The pencil line denotes where the paper should be cut, and if the crank case has been pressed hard enough there will be a slight impression on the paper, with the result that no difficulty will be experienced in cutting out a washer of the correct shape.
Adopt the above procedure in the case of washers for all such joints as the timing cover, magneto-drive cover, and the cylinder base. When fitting the washers, coat their surfaces with gold size or one of the jointing mediums sold for the purpose. All old jointing compound must, of course, be removed if a proper joint is to result.

245. Marking out paper washers by impression can be done effectively by putting a thin piece of cloth on the table beneath the paper on which the part is to be pressed. In this way a clear impression is left on the paper. If thick cloth is used the paper will be pulled out of shape.

Worn Cam Levers
246. If, after the tappets have been adjusted carefully (see Paragraphs 267-269), a big clearance soon develops, the odds are that there is trouble with the cam levers or rocker ends. A cam lever which follows its cam by means of a roller bearing certainly sets up less friction and is less susceptible to wear, but a point of weakness is the pin securing the roller. On the other hand, with the plain type of cam lever, once the case hardening has worn through further wear is very rapid, and the lever should be replaced with a new one.

Dismantling the Timing Gear
247. Before removing the timing cover from the engine, it is as well, as a precaution, to make certain that you know the setting of the timing. After the securing nuts from the timing cover have been removed, a few light blows direct with a rawhide or wooden mallet around the edges of the cover will free it and enable it to be pulled off. N ever insert a screwdriver blade between the faces in order to lever off the cover, for this will ruin the oil- tightness of the casing.
Quite often the cam pinions will be found to be following the cover when the latter is drawn off, owing to a vacuum set up in the spindle bushes by the film of lubricating oil. Before removing the cover very far, therefore, look down through the crack, and with the aid of a knife or clean hacksaw blade, push the cam wheels back into their proper places. When the cover is off, assuming that the pinions have not been disturbed, make sure that the timing is marked. If it is not marked, it is easy enough to scratch lines on the teeth that are in engagement. A scriber, which is a tool with a specially hardened point for scratching lines on metal, is the best instrument to use for this, or, failing a permanent marking, a pencil will. provide a temporary guide to the setting.

Valve Timing
248. If the valve timing of an old engine has been upset, the correct timing is almost certain to be obtained if the engine is' revolved until the piston is exactly at the top of its stroke and the timing pinions meshed so that the inlet valve is just about to open and the exhaust valve about to close. For the method of ascertaining the exact position of the piston, see Paragraphs 325-327, on Magneto Timing.
In this connection, modem engines can be timed by the same method so long as it is remembered that generally the inlet valve should open very slightly before top' dea9 centre and the exhaust valve close very slightly after top dead centre.

249. Converting the degree method of timing into inches or millimetres of piston travel is difficult for anyone without very considerable knowledge of mathematics. A description as to how this may be accomplished, and full details with regard to timing an engine in degrees, will be found in the chapter under that heading in "The Motor Cyclist's Workshop," uniform with this volume.

250. The object of the three or more keyways provided in the mainshaft pinion is to enable an accurate valve timing to be obtained, and the one to be used is that which allows a timing nearest to the setting recommended by the manufacturers. It is not intended that these keyways shall be used to alter the timing, and this should certainly not be done where a standard cam is employed.

Oil Leakage
251. Incomplete release of crank-case pressure is among the possible causes of oil leakage at the crank-case joints. Disconnect any external lubricating pipe from the crank-case breather, and having unscrewed the breather see that the ball (or disc) in the valve is operating freely and that neither the passage in the breather nor the pipe is choked.
 
Checking Flywheel Alignment
252. The easiest way to check whether the flywheels are running tree is to mount them in the crank case and bolt up the crank-case halves; then note whether they run perfectly freely. This is a rough-and-ready test which will meet all normal requirements.

Engine Bearings
253. It is quite in order for the connecting-rod to have a small amount of side movement. Ten thousandths of an inch is about the minimum to be allowed between the roller cage (or the big-end eye) and the flywheels, while as regards maximum play, on a normal sports or touring engine up to 1\8 in. side float may be safely ignored, provided the connecting rod does not foul the flywheels; with a racing engine, however, 20 thou. should not be exceeded. There should be no trace of up-and-down play, but a small amount of side-play (approximately 1\32 in.) on the mainshaft is permissible.

254. To test roughly the connecting-rod bearings of engines with detachable cylinder heads without removing the cylinder barrel, proceed as follows: Obtain an ordinary household rubber suction cup of suitable size and, after washing out the crank case with petrol or flushing oil, stick the cup on the top of the piston when the latter is at the top of its stroke. Hold the engine sprocket firmly (so that any main-bearing play does not confuse matters). and pull and push alternately with the suction cup, which is, of course, gripping the piston. Any up-and-down play will easily be felt.

Plain Bearings
255. A plain mainshaft bearing should be a tight press-fit in the aluminium crank case. If it works loose so as to revolve with the shaft, the oil holes will probably cease to register and the housing will be damaged; seizure, too, is likely. The steps to be taken to remedy matters depend upon the condition of the housing.
If the housing is not appreciably worn a satisfactory repair can sometimes be made by lightly tinning the outside of the bearing with solder before pressing it back into place, but if the housing is badly damaged it will be necessary to have it bored out and fitted with an oversize bush or built up by' welding, or by means of aluminium solder, and then bored out to the correct size for the standard bush.

256. The simplest way of fitting a new little-end bearing in the connecting rod is as follows: Obtain a piece of tubing a little longer than the bush, and just large enough to contain it; open the bench vice (with lead clams over the jaws) wide, and proceed to line up between the jaws (1) the piece of tubing, (2) the little end of the con-rod, and (3) the new bush; then tighten up the vice so that the jaws hold all three lightly together.
Next check over the alignment, making sure that the tubing fits flush against the little end, but does not foul' the old bush; all that is now necessary to complete the job is to tighten up the vice slowly and surely until the new bush is forced into position and the old bush forced out into, the tubing on the other side-all in one operation. The bush must, of course, be either scraped in or reamed out to fit the gudgeon-pin.

Removing a Ball Race
257. Removing a ball race often presents a puzzling problem. The best way, and in some cases the only way, is to heat the housing, which is nearly always an aluminium alloy; the greater expansion rate of the aluminium will allow the ball race to drop out. Warm the housing only -not the race- by careful exposure to the flame of a gas-ring or blow-lamp for a very brief period, and tap the housing on the bench, when the race will drop out. The new race can be dropped into position while the housing is still hot.

General Engine Vibration
258. A small amount of vibration is unavoidable with a single-cylinder engine. If, however, the vibration appears to be excessive the engine bolts should be tested with a spanner; they may be loose, and the holes in the engine plates and in the crank case through which the bolts pass may have worn oval. Also see that the primary chain is correctly adjusted (see Paragraph 555), and that the chain and the sprockets over which it runs are in good condition. If the points are in order, then the trouble may be due to a loose flywheel, a worn engine bearing, or even conceivably to a broken frame.

Engine Cooling
259. When in air-cooled engine is running with the machine stationary it is only being cooled by direct radiation and not by conduction by means of a forced draught. The amount of cooling obtained in such circumstances is extremely small, and it is advisable, therefore, to avoid running the engine for long periods in neutral.

Overheating
260. Overheating may be brought about by a variety of causes, but can usually be traced to faulty piston rings, a worn cylinder, worn piston, a weak mixture, choked silencer, under-lubrication, or incorrect valve or magneto timing. The rings should be replaced if they are discoloured or their gaps exceed 40\1000 in. when the rings are inserted truly in the cylinder bore, while if the cylinder is worm or badly scored (see Paragraphs 234, 235), reboring and an oversize piston would be advisable. Incidentally, it should be remembered that a crank case normally runs fairly hot owing to the transference of heat from the cylinder, and the fact that it feels warm to the fingers need cause no alarm so long as the engine performance is satisfactory.

A Radiator Repair
261. It sometimes happens that after long usage a radiator on a water-cooled machine springs a leak some- where in the middle of one of the honeycombs. Even if the hole is accessible the copper may be so weakened by gallons of hard water passing through it that the mending of one little leak may start another. The best thing is to get some copper tubing which will just push through the comb. Then saw off a length sufficient to reach from front to back of the radiator; tin it over with solder until it is just a push fit, and, having scraped the honeycomb until it is clean, push the tube through and apply a small "crow's beak" soldering iron and a little solder at each end. The honeycomb will now be watertight, and the air will pass through almost as freely as before.

Anti-Freezing Mixture
262. In cold weather damage due to freezing of the water in the radiator may be avoided by using either a special anti-freezing mixture or a solution consisting of glycerine and water. A mixture of 10 per cent. glycerine and 90 per cent. water freezes. at 27° Fahrenheit, while a 30 per cent. solution freezes at 12° F., and a 40 per cent. solution at 0° F. The two liquids should be mixed by volume. No ill-effects will result from its use.

Grinding-in Valve Gear
263. When the valve has a slot in the head, a screwdriver can be used for turning the valve. Most modern valves, however, need a special tool; this may take the form of a three-jaw chuck to grip any stem, which can be purchased quite cheaply at a tool stores; a special chuck to take the particular size of split collets (this is usually obtainable from the engine manufactuers) , or a device made out of a tube that will just fit over the valve stem. The last named should have a set-screw in the side which can be tightened up on the stem, and a rigidly attached tommy-bar at the other end. Pliers should never be used to hold the stem, for not only will the results be unsatisfactory but the stem will probably be seriously damaged.

264. A sound plan when grinding-in is to place a light spring beneath the valve head, so that when pressure is relaxed the valve will spring off the seating. Smear grinding paste lightly over the face of the valve. Do not rotate the valve a complete turn, and above all never spin it round and round. Rotate the valve about half a turn, first one way and then the other. Every now and then redistribute the paste evenly over the surface. When the faces begin to appear smooth and bright, change to a finer grade of paste, if available. Finally, wash the seatings and the whole of the valve housing thoroughly with petrol. Many riders, among them expert tuners, are satisfied with their labours so long as there is a definite, continuous bright ring on both the valve and the seating, but the majority prefer to have each valve bedding down over the whole of its face. For the meticulous a good test is to see whether the valve, retained on its seating by one or more of its springs, will hold petrol.

265. Excessive grinding-in of a valve causes the seat to be badly worn away, and the effective lift of the valve to be reduced, which, in turn, spells loss of efficiency and even overheating. Therefore when a valve or valve seat is seriously pitted it is advisable to have it trued up by a competent mechanic, and not to endeavour to remedy the trouble by patient grinding-in. Even with normal grinding-in the valves in time will become pocketed or masked; this point should be borne in mind, and any serious pocketing should be removed by having the metal that is causing the "shrouding" cut away, or the old seats machined away and new replaceable seats fitted in their place.

266. After a valve is ground-in the tappet clearance should be checked, since it is automatically reduced as the result of the grinding-in.

Tappet Clearances
267. Correct tappet clearance is important, since too much clearance not only sets up a clatter, and causes undue stress upon the valves, the valve seatings (due to the "hammering" effect) and all working parts, but also alters the valve timing, owing to the tappet or cam lever not following the cam contour accurately. Too little clearance on an exhaust valve will bum out the seat. Keep the clearances adjusted, therefore, in accordance with the maker's instructions.

268. In any engine, both the cylinder and the valve stems expand when the engine gets hot, and both with a side-valve or overhead-valve unit the expansion of the cylinder causes an increase in the valve clearance. In both cases, however, the expansion of the valve stems tends to counteract this effect. With an overhead-valve engine the counteraction is small, and the valve clearances invariably increase slightly as the engine temperature rises; but with a side-valve engine the longer valve stems occasionally expand more than the portion of the cylinder between the valve chest and the crank-case mouth; while with an overhead camshaft the camshaft is mounted directly on the cylinder and therefore the chief factor is the expansion of the valve stems; fairly large clearances are necessary with a camshaft engine used for high-speed work.

269. If feeler gauges are not available, an excellent guide on an o.h. v. engine fitted with pushrods, so long as there are no pushrod return springs, is to set the adjustment so that the pushrods can just revolve freely. If "thimbles" are fitted over the ends of the valve stems, the adjustment can be set so that these can just be turned freely.

Valve Springs
270. Much ingenuity is often devoted to the construction of special instruments to depress valve springs, especially for use on o.h. v. engines. If the springs are not very powerful, a simple tool can be made out of a piece of tubing of slightly smaller diameter than the spring collar, with a tommy-bar handle and long slots cut in the side through which the cotters can be removed. But usually the simplest thing to do is to buy one of the ready-made tools specially for the job. They are not expensive, and generally save time, temper, and knuckles.

271. Loss of performance on a hot-stuff engine can often be traced to the valve springs having become "sluggish" or the breakage of an inlet valve spring in a concealed position; the cure is to fit new ones.

Fitting Valve Springs
272. For ease of attachment, carry valve springs tied up in compression. This is done by compressing them in a vice and tying them up longitudinally with wire, but see that the wire is not so thick that it prevents the springs being fitted! When required, the compressed spring is placed over the guide and stem, the collar and collets fitted, and the wire cut and finally pulled away. Removal can be facilitated by levering up the spring to free the wire. Threading the wire through a coil or two will prevent it slipping round.

273. A method which will generally overcome the difficulties attached to the renewal of a broken side-valve spring by the roadside is as follows: Remove the valve cap and place on the valve head a hexagon nut of a suit- able size, "borrowed" from, say, a wheel spindle; this, with the valve cap replaced, and screwed down finger- tight, will keep the valve on its seat. Then attach a length of stout wire to the valve cap and twist the other end up, leaving a loop through which a screwdriver may be inserted with the point under the valve collar. The loop of wire will serve as a fulcrum on which the screw- driver can bear down, thus compressing the valve spring. If a spare valve spring is carried in ttle toolbox, all ready compressed and bound up, it will be an easy matter to fit it; if no spare is available, the two halves of the spring should be replaced with their ends together; this will generally allow the machine to be ridden until a new spring can be procured. Do not forget the nut under the valve cap.

Removing Valve Caps
274. It is sometimes difficult to remove the valve caps on side-valve engines. In this case try thoroughly soaking a piece of rag or cotton-waste in paraffin, turpentine, or. better still, one of the special penetrating oils, leaving it on the valve cap overnight. Then obtain a long, well- fitting spanner (preferably a ring spanner) with which to grip the cap. arid give a series of sharp light taps on the extreme end of the spanner with a not-too-heavy hammer. Another method is to warm up the cylinder and then pour cold water into the hollow of the valve cap, so causing it. to contract.

Valve Guides
275. In general terms it may be said that replacements are needed when the clearance between a valve and its guide exceeds ten or twelve thousandths of a inch. The clearance may be measured by inserting pieces of wire between the valve and its guide and checking off the diameter of the wire with a micrometer.

276. The valve guides of all modern engines are a push-fit in the cylinder, and it is bad practice to drive them out with a brass or copper rod. There is always the danger of the valve chest or the cylinder head being cracked. It is far better to rig up a simple withdrawal tool. 'Obtain a long cheese-headed bolt, cut two small flats on the threaded end, and insert the bolt in the guide from the valve seat end. Then at the other end on the outside fit a distance-piece over the guide, a washer over the bolt, and finally a nut. Screw down the nut, holding the bolt stationary by means of a spanner engaging on the flats. The guide will thus be forced out of position. The head of the bolt should, of course, be of a diameter slightly smaller than the external diameter of the guide.

277. When fitting a new guide, a similar method can be used with the bolt threaded through a special washer so made that it beds down on the valve seat. This washer can be made from the head of an old valve. The position of the tool will, of course, be reversed, but the procedure is the same. After a new guide is fitted it is essential to grind in the valve-sometimes even to have both the valve and its seat trued up.

278. It is little less than useless fitting a new valve in an engine if the valve guide is badly worn, for the stem of the new valve will soon be in as bad a state as that of the old one; both the valve and the guide should be replaced.

Valve-guide Lubrication
279. The simplest method to ensure lubrication of the inlet valve guide on an old-type engine where no proper means is provided is to mix a small quantity of one of the special upper-cylinder lubricants or ordinary tt touring engine oil with the petrol. This will often cure a puzzling "squeak" in the engine. The valves, if removed at any time, should have their stems smeared with graphite grease before being replaced.

280. Another less simple but more efficient method, which is applicable to o.h. v. and o.h.c. engines, is to drill a small hole through the valve-guide housing and valve guide, and fit in it a thin copper pipe. Oil can then be led from the lubrication system of the rocker-boxes or overhead camshaft, from the crank-case breather, or from a separate little oil tank, mounted underneath the petrol tank.

[a10 gf]

"slight pinking does not affect the power output -only the nerves"   

[RichardL]

This is great. A little lengthy for me to have read completely, yet, but full of interesting and/or useful advice. For example, the text has already busted me for tapping out paper washers against aluminum openings.

Richard L.

[a10 gf]

CHAPTER XXIX: WORKSHOP AND USE OF TOOLS

(Notice from DCHM (Dept. of Can't Happen to Me): keep a fire extinguisher available, always located within reach, check regularly that it is in working order)

First Essentials
673. Three essential features if good work is to be done in a workshop are (1) a good light, (2) a sturdy, rigid bench, and (3) a suitable vice set at the correct height. It might be said that there are two other essentials, patience and tidiness, but these concern the man and not the shop in which he works.

674. Wherever possible the bench should face north, for this will ensure the best light, and should have its legs set in concrete or at all events properly fixed to the floor. No one can file truly if the bench shimmies and shakes. Needless to say, the vice must be rigidly fixed to the bench.

The Height of the Vice
675. For good workmanship one must fix the vice at the proper height. It should be so arranged that the top of the jaws are level with the user's elbow. To raise a vice that is too low, mount a steel packing plate between the base of the vice and the bench.

Filing
676. Files cut only on the forward stroke, as will be apparent from an examination of their teeth. Therefore apply pressure on the forward stroke only. The correct method of holding a flat file that is being used for heavy work is to grasp the handle in the right palm with the thumb on top and the first finger along the handle; the left palm should be placed flat on the other end of the file.

677. To use the file, stand with the left foot in front of the right, keep the right arm close to the side, and sway the body forward with each forward stroke. Do not push the file straightforward, but thrust it slightly to the right.

678. When using a small file hold the end of the file between the thumb and first finger of the left hand.

Soft Metals
679. Before being used on brass, aluminium, lead, solder, or other soft metals, a file should be well filled with chalk. This will delay for a long time the choking of the teeth with metal.

Shouldering a Rod
680. When it is necessary to shoulder a rod by filing, the following procedure will enable a neat result to be obtained. A loosely fitting washer should be threaded over the rod, and the latter placed upright in the vice with the washer resting on the jaws. The rod should be adjusted vertically so that the limit of the required shoulder is exactly in line with the upper face of the washer. The file, which should preferably be of the "safe-edge" variety, will thus be able to rest on the washer, and can be used evenly round the rod, with a see-saw motion. The washer will run round under the action of the file, protecting the jaws of the vice, and at the same time allowing a good square shoulder to be obtained.

Drilling
681. Two types of drill are normally used by the amateur: first, the hand drill which takes drills up to 1\4 in. diameter, and, secondly, the breast drill, which is for heavier work and accommodates drills up to 1\2 in. As with all tools, it pays to buy a good article. In the case of breast drills avoid those with two-jaw chucks; these will not hold the drills firmly. A drill with a three-jaw chuck is needed.

682. Morse twist drills are the type of drills that should be purchased. Buy those made of high-speed steel in preference to cast steel, which will not stand up to hard usage so well.

683. To confine the drill to its proper spot, make a small indentation at the correct point in the metal to be drilled by means of a hammer and centre-punch. Then lubricate the drill with turpentine (use no lubricant for brass or phosphor-bronze) and rotate the drill steadily, taking care not to rock it.

Large Holes
684. If a hole 3\8 in. or more in diameter has to be drilled, first drill a "pilot" hole with a 1\8 in. drill; this will prevent the big drill from wandering as well as make the work lighter. Wherever possible a breast drill should be used horizontally.

Drilling Glass
685. It is not often that one wishes to drill holes in glass, but sometimes it is useful. Actually the task is very easy. A piece of copper or brass tube of light gauge and of the required outside diameter is selected. The glass is lightly clamped between two pieces of soft wood, in the upper of which a hole of the correct size has been bored, and set over the exact spot where it is desired to drill the glass. The brass tube should have two or three nicks filed in one end; it is then loaded with water-mixed valve-grinding compound, and rotated fairly fast with a brace, using light pressure, through the hole in the wood. Water and compound should be fed to the cutter as it progresses, and a clean hole will result in quite a short time.

Substitute for a Lathe
686. Not everybody owns a lathe, but for small jobs a drill may be rigged up as a very useful substitute. Mount the drill in a vice, and using the jaws of the drill as a chuck to grip the object which is to be worked upon, rotate the drill with one hand and use a file, emery cloth, or whatever is needed with the other. A valve head, for instance, may be polished very readily in this manner.

Removing Sprockets, Nuts, and Studs
Sprocket Drawers
687. A proper withdrawing tool is desirable for sprocket removal. There are other methods, but unless care is taken there is the possibility of damage being done either to the shaft on which the sprocket is mounted or to the bearings of that shaft. The best type of sprocket drawer is that having three prongs; if there are only two prongs there is always the probability that the tool will cant over when pressure is applied to the central stud and damage be done to the end of the shaft. Where a suitable sprocket drawer is not available, more often than not it is possible to borrow one from a local garage on the payment of a few pence.

688. When removing an engine sprocket never let the stud of the withdrawing tool bear direct on the end of the engine shaft. Place between it and the shaft a piece of copper or brass, since otherwise the stud might damage the small indentation which will be found in the end of the shaft and which, incidentally, is important for lining-up the flywheels.

689. Should a sprocket appear welded to its shaft, give the end of the stud on the sprocket drawer a few light taps with a hammer. This, so long as the stud has previously been properly tightened, will generally free the sprocket.

690. Another quite satisfactory method is that of jarring the tapers, which has been described in Paragraph 573.

Undoing Tight Nuts or Studs
691. A method similar to that adopted with an obstinate sprocket can be used to " persuade " a recalcitrant hexagon-headed set-screw. Always use a properly fitting spanner and try the effect of gently tapping the handle of the spanner; if this does not have the desired result, don't hammer the spanner until the hexagon head of the screw is distorted (or even sheared off), but give the end of the screw a few light blows. This will break the "adhesion", and make the screw easy to remove in the normal way.

692. If a nut is causing the bother; and not a screw, place a brass or copper rod (commonly called a "drift ") square against the top and give this drift a few taps. (See also. Paragraph 701.)

Removing, a Broken Stud
693. When a stud breaks off,there are several methods whereby the remains can be extracted from the crank case, timing chest, or whatever the component is. If a short length is protruding the best method is carefully to file two parallel flats on the protruding portion. Then give the end of the stud a few light taps with a hammer to free its threads and, finally, unscrew the stub with a spanner. Never attempt to use a monkey wrench, for this will probably smash the protruding portion and make matters worse.

694. More often than not, however, studs have the awkward habit of breaking off flush. In this case either a slot can be cut in the end with a chisel, so that a screwdriver can be used, or a hole can be drilled down the centre and a squared rod driven in, the rod finally being rotated by means of a spanner.

695. Another method which requires great tare is to drill a hole in the centre of the stud and make this hole of such a diameter that all the stud is drilled away with the exception of a small sheath-like portion which can be picked out with a sharp, pointed instrument.

Spanners
696. The handle of an adjustable spanner should be turned in the direction of the open end of the jaws; if it is used the other way the jaws are likely to become strained. Similarly, with a set spanner that has the jaws at an angle to the shank, there is both a correct and incorrect way.

697. To turn an awkwardly placed nut without a box spanner -say, a cylinder base nut- fit the correct end of a double-ended spanner over the nut in an upright position, then grip the other end in an adjustable spanner and turn. This, while effective, is hardly good for the spanner.

698. When carrying out maintenance or repair work in the garage, it is unwise to use tools more powerful than those carried in the kit for operations which may later have to be carried out on the road. For instance, spindle nuts should not be tightened with a long spanner that is normally left at home. They should be dealt with by the kit spanner, hammered up if necessary by another kit spanner. A big shifting-spanner is well worth carrying.

699. A set of ring-spanners to fit obstinate nuts can be invaluable. More leverage can be obtained with this type of spanner than With practically any other, without fear of burring the nut or opening up the jaws. Such parts as sticking valve caps and sparking plugs can be quickly dealt with, provided that the ring spanner is exactly the right size. All set spanners will be found to be remarkably efficient provided that they are a real close fit on the nut.

700. A set of the stubby "universal" box-spanners will also be very useful. These little tools, about 3\4 in. in depth, will get into the most inaccessible comers and can easily be rotated by their special tommy-bars and/or braces.

701. An extremely useful gadget, invaluable when dealing with obstinate nuts or bolts, can be made from eighteen inches of 1 1\4 in. steel tube. Flatten one end out slightly, to a distance of six inches or so from the end. By slipping the end over a spanner, terrific leverage can be obtained; be careful, however that the leverage is not too terrific!

702. When a nut seems disinclined to screw on to the end of its bolt, a good plan is to try turning it anti-clockwise for part of a turn and then clockwise in its correct "screwing-on" direction.

703. Nuts and set-screw heads, the corners of which have become damaged by a slipping spanner, may in many cases be filed to fit a smaller size of spanner.

Eliminate Projecting Threads
704. When fitting or replacing mudguard bolts or set-screws, washer them or shorten them if necessary, so that they end just flush with the nut or other thread, as the case may be. This will eliminate projecting threads, which usually corrode and make removal difficult. Before fitting, work well into all threads a good graphite grease. For such a purpose graphite grease is much superior to oil.

Screwdrivers
705. A screwdriver should not be filed to a chisel edge, but to a rectangular end, parallel for about one-sixteenth of an inch up the shank. This will leave more metal at the tip and will stop the screwdriver from jumping out easily. One screwdriver, even when properly made, cannot satisfactorily fit all screw heads, so have two or three sizes in the rack.

706. A stubborn screw can usually be removed by placing the screwdriver in the slot and giving its handle a few hard taps with a mallet.

707. Obstinate set-screws with slotted heads may be loosened (and also tightened) by the use of a spanner to help the screwdriver. The latter should be pressed home with one hand and turned with an adjustable spanner held in the other hand with its jaws gripping the flat faces tightly near the point of the screwdriver.

708. Another method of securing leverage is to use a carpenter's brace with a screwdriver bit.

709. Bolts with inaccessible heads which persist in turning when attempts are made to tighten their nuts should have a good screwdriver slot cut in the threaded end of the bolt. The latter can then be held with a screwdriver while the nut is tightened with a spanner in the ordinary way.

Slotting a Bolt
710. The simplest method of cutting a screwdriver slot is to fit two blades in a hacksaw frame, so that the resultant cut will be wide enough to take a screwdriver blade properly; and, what is more important, the edges of the slot will be true and not likely to let the screwdriver slip.

General
Hacksaws
711. Like files, hacksaw blades cut in one direction only. Always fix the blade in the hacksaw frame so that the teeth point away from the handle, and tighten the blade until it is held just taut. The method of using a hacksaw is much the same as that adopted in handling a file. Hold the handle in the same way, but curl the left hand roufld the front bend of the frame. Slow, deliberate strokes should be the maxim. No lubricant is necessary, by the way. Wherever possible, work with the hacksaw horizontal.

712. The most suitable blades for motor cycle work are probably the 10 in. with twenty-two teeth to the inch, while as for the frame the ordinary adjustable type is excellent so long as it has a rigid handle.

Chisels
713. A chisel should be gripped with the thumb and four fingers of the left hand, the thumb being pressed upwards against the chisel. The first thing to do with a flat chisel is to grind off its corners, otherwise the chisel point would probably break. When endeavouring to keep a level cut, do not make the mistake of laying the lower face of the point flat on the work. There must be a small angle of relief.

714. When a chisel is being hardened, the degree to which it should be tempered depends to a large extent on the composition of the steel. However, assuming that the usual 1 per cent, carbon steel is employed, the tool should be heated until the oxide formed takes on a brown tint, and then dipped into water. The actual rate of cooling has very little influence, but the oxide tint must be very carefully watched if the best results are desired.

Scrapers
715. A flat scraper can be made from a flat file, which should be made red hot and then hammered out thin at the end. This drawing out, or thinning down, is not so easy as it looks, but with a little care a fairly workmanlike job will result. Then, with the aid of a grindstone, grind the end into a slight curve. The scraper should then be hardened by heating it to a bright red and plunging it into cold water. Let the steel cool right off before withdrawing it from the water and then carefully carry out the final grinding, and lastly sharpen it on an oil stone.

Pliers
716. A tool that is of great utility for retrieving small parts that have accidentally fallen into the crank case, gear box, or petrol tank when overhauling, is a pair of finger pliers. These can easily be made from a crocodile clip (such as is used in the construction of radio sets) and a length of stout wire. To the arms of the clip should be soldered lengths of wire, with loops formed in the opposite ends to complete the "scissors" effect.

717. Although "wired-on" accessories or additions are bad practice, it often happens -perhaps during a trial- that certain items suffer damage and need temporary support. To wire on, say, a damaged exhaust pipe may seem simple enough -until the last turn of the pliers cuts through the strands.  It is not generally realized that there is a right and wrong way to essay even this simple task. Assuming that two or three turns of wire have been made, the usual method of grasping the ends with pliers is correct, but the important point to watch is that, during the final twisting, a strong and even pull is exerted on the wire until the required tautness is obtained. Neglect to pull on the wire results in the entire strain being put on the twist, and not on the wire encircling the damaged component.

Bifurcated Rivets
718. Bifurcated rivets often come in extraordinarily handy for repairing broken straps, tool bags, etc. When leather is the material to be riveted, the bifurcated rivets can generally be tapped through satisfactorily if a piece of soft wood is used as a support. Having driven one of them home, place the end of a screwdriver blade in the slot, and bend the ears over, clenching them by tapping their ends. A point of great importance is never to tap down the centre hard, because, in this case, the ears will be cracked. The whole question of riveting is dealt with very fully in "The Motor Cyclist's Workshop", together with all jobs normally tackled by the amateur mechanic.

Tin-snips
719. The usual method of cutting a sheet of heavy-gauge tin is a rather tiresome job. A good plan is as follows: Tighten up one handle of the tin-snips in the vice, and then feed the tin to the snips, working the free handle up and down with the right hand. In this way more pressure can be put on the tin-snips and a straight line can be followed without difficulty.

An Anvil
720. A very useful little anvil can be made for the amateur's bench from an old 2-lb. flat-iron. Cut off the handle where it enters the base and drill and tap a 5\16 in. hole about 1 1\2 in. from each end. Drill two holes in the bench to register with the holes in the iron and pass two bolts through the bench and about three-quarters of an inch into the iron.

Coin Measurements
721. Although a set of rules should always find a place in the amateur mechanic's equipment, it sometimes happens 'that measurements are required without the necessary items being available. In such instances it is worth knowing that the following coins represent certain definite measurements:
One penny: 1\10 of a foot in diameter.
A sixpence: 3\4 in. diameter.
Half-crown: 1 1\4 in. diameter.
Five halfpennies or three pennies weigh one ounce.

[a10 gf]

CHAPTER XIII IGNITION I

Preliminary Tests
303. Failures in the ignition system may be divided into three possible sources of trouble -the magneto or coil and battery, the high-tension lead or cables, and the sparking plug. A somewhat exciting but certainly the quickest way of finding out whether the magneto is functioning is to place one finger on the plug terminal and at the same time kick the engine over. If a shock results, then the magneto or coil at all events is working properly. Such a shock will make one hurriedly and quite involuntarily withdraw the finger, but will not do one any injury. If, however, there is little more than a tickling sensation or not even a suspicion of a tingle, either the magneto or high-tension cable is at fault.

304. A rapid glance will show whether the h.t. cable is adrift at the magneto end, whether it has chafed through against, say, the petrol pipe, or burnt through on the cylinder head, or whether it is perished. Should the cable be leaking by reason of one of these faults, arrange it so that it i kept clear of all metal parts of the machine. This can usually be accomplished either by twisting the wire and then replacing it (still twisted) on the plug terminal or by screwing up the plug terminal so that it holds the cable out of harm's way. Fit a new cable at the earliest opportunity. Never run with a cable that shows signs of being perished -cable is cheap enough and easily fitted. Always arrange the cable so that it cannot flap about; keep it away from the frame, if possible.

305. If a shock is felt at the "finger test" described in 303, and therefore the magneto is functioning properly and the h. t. wiring is in order, but the engine does not fire, one must turn one's attention to the sparking plug. It may be "burnt out" or "oiled up". In the first case the insulation will have broken down, though it is unlikely that a completely "dead" plug will result from this cause; in the second the insulation will have become "bridged" by a film of oil, carbon, or soot, thus causing a dead short and no spark at the points. (See Paragraphs 339-355). Make sure that the plug points themselves have the correct gap. (See Paragraph 149).

Cut-out
306. A magneto "cut-out" simply consists of a device for earthing the central retaining stud of the contact breaker. Hence any bared portion of the wire touching an "earth" will result in a direct short for the magneto, which will not harm it but will result in no spark. The usual arrangement is for an insulated contact spring to be attached to the contact-breaker, this spring being connected by an insulated wire to some form of switch mounted on the handlebars or the frame of the machine. A magneto "cut-out" should not be confused with the automatic dynamo cut-out, which is a separate instrument on its own account. (See Paragraph 188.) If a magneto cut-out is fitted and the magneto is not operating properly, first try the effect of detaching the insulated cable from the contact-breaker, or, if the cut-out is incorporated in the cover of the contact-breaker, remove the cover. Sometimes the wire becomes chafed, or detached at the switch end, resulting in a baflling problem to the inexperienced.

A Theft-prevention Tip
307. Incidentally, while upon the subject of a cut-out, a very simple thief-hindering device consists of an extra contact-breaker cover with a small piece of spring, such as part of a cycle trouser clip, soldered to it in such a way as to bear on the central stud when the spare cover is fitted, thus constituting an earthing switch in the same manner asa cut-out. It is seldom that prospective thieves have time for fault-finding.
Another scheme sometimes adopted is to remove the float of the carburetter, but, of course, it is absolutely essential to see that the float is perfectly clean when it is put back. Only in a few designs, however, is it possible to remove the float easily and quickly.

The Contact-breaker
308. To revert to the faulty magneto, the second thing to suspect is the contact-breaker. Remove the contact-breaker cover, rotate the engine, and watch whether the platinum points open and close. It is easy enough to be misled-not on whether they open, but as regards their closing. They must close completely, so that there is not even the fraction of a thousandth of an inch between them. If there is the slightest doubt on this point, slip a piece of white paper behind the points and examine them fairly and squarely in a strong light. When fully open the points should separate to 12\1000 ths in. in the case of all magnetos except the M.-L., which demands 10\1000 ths, and the Villiers flywheel magneto, which should have its points set to 1\64 in.

309. If the rocker arm is sticking, remove the contact-breaker. To do this, undo the central stud with the special magneto spanner and prise the contact-breaker off either by gentle leverage with a small screwdriver (or two small screwdrivers, one either side), or by waggling the central stud after it has been unscrewed but not pulled right out. Then undo the bow-spring attached to the rocker arm. never try to pull off the rocker arm with the spring in position. If the spindle on which the rocker arm works is rusty or dirty, polish it with very fine emery cloth, or the striking surface of a safety-match box. Should there still be signs of sticking, ease the fibre bush in the rocker and by rubbing it internally with a strip of sandpaper wrapped around a match stick. Before finally replacing the rocker and smear the spindle with oil; use only the smallest possible trace, for there must be no chance of oil finding its way on to the platinum points.

310. Some magnetos have a fibre plunger working on a face cam instead of the more usual rocker arm. In this case the plunger, if it shows signs of sticking, should be eased very carefully with sandpaper until it is a perfect sliding fit.

311. Sometimes the fibre pad on the rocker arm swells slightly owing to damp, and the points, although perhaps closing on full retard, remain very slightly open on full advance. In this case the engine will run properly on full retard, but as soon as the ignition is advanced eight-stroking or general misfiring will set in. The cure in this case is to ease off the pad.

312. An occasional and usually regular misfire on an elderly machine fitted with a C.A.V. magneto is due as a rule to the fibre roller at the end of the rocker and having worn unevenly on the inside. In this case do not try to improve matters by reaming out the roller, hut fit a new one at the earliest possible moment.

313. One other little matter of importance to purchasers of second-hand machines or magnetos: examine the bush on the contact-breaker for wear -the cost of a new bush is only pence, while that of new platinum points is a number of shillings.

Contact-breaker Points
314. For easy starting and good slow running, not only must the platinum points be set to their correct gap and close properly, as mentioned on the previous page, but they must be clean and bed down properly. A black, sooty appearance denotes the presence of oil, petrol or dirt of some sort. In this case wipe them clean with a piece of soft clean rag. Should they be burnt to a yellowish or whitish appearance, a faulty condenser is probable; this point becomes practically a certainty if there is heavy sparking at the points when the engine is running and the points are clean. A bluish tinge denotes the presence of water.
To make the points bed down properly, filing is necessary, using for the purpose a magneto file or, if this is not available, a fine nail file. Remove as little as possible and that only with great care. Afterwards the gap, of course, requires resetting.

315. Often the points are not of platinum but of tungsten. In either case the screws are only tipped with the metal, which is welded on. After considerable use, tungsten points oxidize and require polishing with smooth emery cloth and oil, or a safety-match box and oil. Naturally all traces of both the abrasive and the oil must fully be removed. If the points are found by some ill-chance to have burnt right off, repeated filing of the ends of the steel screws will enable one's journey to be completed.

The Condenser
316. The condenser is a small device usually composed of a number of tin-foil plates with mica insulation between them, and is capable, broadly. speaking, of storing a small charge of current for a short time. Its function is to trap the extra current induced in the primary coil when the platinum points of the contact-breaker are opened; this current would otherwise tend to cause continuous, heavy sparking across the platinum points, to their detriment. Such sparking is a certain sign of a faulty condenser. Starting may also be difficult. The only cure is to have the condenser replaced by the manufacturers.

Earth Brush
317. Assuming everything is in order regarding the rocker arm and the points, yet the magneto still fails to function properly, carefully clean the back of the contact-breaker, its carbon brush and the end plate of the magneto upon which the brush bears. Use a clean rag for the purpose. The carbon brush mounted in the back of the contact-breaker -the earth brush in other words- is not absolutely essential, for the current will normally find its way all right through the grease-packed armature bearings if the brush is missing; but its sound condition and presence do make for good starting and perfect firing.

Replacing the Contact-breaker
318. When replacing the contact-breaker -which is the next task in order of sequence- be sure that the little key goes home in its keyway. The central stud should be screwed up until it is just tight; do not use brute-force or the stud may fracture.

The High-tension Pick-up
319. Now, if the cause of the trouble has not yet been found, transfer your attention to the high-tension end of the magneto: Remove the brush-holder (to which is attached the h.t. cable). Take care over this, for brush holders are often brittle. Then examine, first, the brush-holder for grease and cracks and, secondly, the brush, which either may be sticking in its holder or be broken. Should the brush-holder be cracked, and not merely dirty, so that the high-tension current runs to earth instead of to the sparking plug, the position is, to say the least, an unenviable one if the machine is stranded at the roadside (which, happily, is more than unlikely). Either the brush-holder must be replaced with a new one or the crack must be filled up with some really effective insulating medium. If there is a wireless shop handy probably some Chatterton's compound will be available. A little of this, melted and run into the crack, should meet the case, or else some thick shellac varnish.

320. Should the trouble be that the carbon brush is sticking in its holder, ease it very carefully with smooth emery cloth or even a fine file. Do not rub away the glaze at the end of the brush, for this gives good conduction of the electricity.

Broken Carbon Brush
321. It is seldom that a brush breaks up and still more seldom that a spare is carried. However, there is an easy way out once the broken pieces have been recovered from the magneto. This latter job can generally be accomplished by a little fishing with a piece of wire dipped in rubber solution. Afterwards the slip ring must be cleaned by inserting a pencil of rolled rag moistened with petrol in the hole for the brush-holder and holding it against the slip ring while the engine is turned over, there should be no oil whatever on the brush-holder or the slip ring.
The old get-you-home scheme in the case of a broken or lost h.t. brush is to fake up a piece of lead pencil. This is a poor sort of substitute, however. It is better to use a small roll of silver paper-long enough to bear lightly on the slip ring and thick enough to remain firmly fixed in the brush-holder.

Stripping the Magneto
322. The previous hints cover almost all the work that can be accomplished by the amateur. If, however, it has been found that the inside of the magneto is flooded with oil, it may be desirable to strip the instrument. First remove the magneto from the machine; then detach the carbon brush-holder and the contact-breaker; next and very important: search round for any little screw which looks as if it might pass through the base of the end castings (generally at the h.t. pick-up end of the instrument) and have its other end close against the revolving armature. This particular screw forms the safety gap, and if not removed has a nasty habit of fouling the slip ring and breaking it when the armature is extracted. This accomplished, undo the screws holding the end plate of the magneto to the plate at the contact-breaker end, and tap the end of the armature spindle to loosen the end plate. Do not attempt to prise off the end plate; this may damage the ball bearing on which the armature spindle runs and will almost certainly spoil the joints. Then before tapping the armature right out of its tunnel, a keeper must be placed across the poles of the magnet. This is to prevent the magnets becoming demagnetized. A piece of soft iron forms the best keeper, but big tyre levers or even a large adjustable will act the part pretty well.
When the armature is out, clean it carefully, also the tunnel. and- the slip ring. If this does not cure the trouble and all the suggestions already mentioned have been tried, the chances are that the repair is beyond the capabilities of an amateur and must be entrusted to the makers or a first-class firm of magneto specialists.

Lubricating a Magneto
323. Once every ten thousand miles a magneto should be stripped and the bearings repacked with grease. This can best be carried out at the maker's service depot, which will at the same time check over the instrument to see that it is in perfect order. If, however, the rider decides to do it himself, the instructions given above under the heading "Stripping the magneto" should be followed. Ordinary grease should not be used; for it may oxidize; instead use a high-melting-point (H.M.P.) grease of known brand. Employ it sparingly; do not pack the bearings so that they overflow.

Magneto Timing
Timing Slipping
324. Slipping of the magneto timing is not likely to occur unless either the two sprockets driving the magneto have been carelessly tightened on their tapers, or the tapers themselves are worn. In the latter case, lightly grind the sprockets on their tapers with a faint application of fine paste.

Checking over the Timing
325. The symptoms of slipped timing are loss of power and often irregular firing, accompanied by violent reports in the silencer. Spitting back may also be experienced. Under these conditions, if the plug appears to be giving a normal spark, the petrol system is clear, and the valve gear is intact and functioning, check over the timing of the spark. To do this, remove the plug and slowly rotate the engine until the inlet valve closes. Then with top gear engaged move the rear wheel round in its proper direction until the piston is at the top of the compression stroke; the position of the piston can be "felt" by inserting a pencil or piece of clean stick through the sparking plug hole. Next, having retarded the magneto control fully, examine the contact-breaker points; these latter should be just separated or just about to separate. If this is not the case, the timing is wrong.

Retiming
326. First remove the magneto chain cover and then the sprocket on the armature spindle, assuming chain drive is used. For this latter work a small sprocket-drawer is desirable, but in a case of necessity carefully lever off the sprocket with two small tyre levers. If gear drive is employed, merely withdraw an intermediate pinion after seeing that the pinion on the armature shaft is properly tightened up. Then set the piston at the top of the compression stroke in the manner described above, and if the maker's timing is that the spark should occur when the piston is at the top of its stroke with the magneto fully retarded (quite a normal touring timing, by the way), turn the contact-breaker round until the points are just starting to separate; then, holding the contact-breaker stationary, press the sprocket home and tighten up its nut; see beforehand that the tapers are clean and dry. It is a good plan, when tightening the nut, to have the rear brake on to prevent the engine turning, or to lock the wheel in some other manner, the engine still being, of course, in gear. The spanner can be tapped round to ensure that the nut is dead tight, but naturally no brute force is permissible. With gear drive set the contact-breaker as mentioned above and merely replace the intermediate pinion after seeing that the magneto pinion is properly tightened up.

327. Should the timing stipulated by the makers be, say, that the spark should occur (i.e., the points just start to separate) when the piston is 7\16 in. before top dead centre (t.d.c.) with the magneto fully advanced, proceed as follows. First advance the magneto control, then set the piston exactly at the top of its stroke and insert a piece of stiff wire into the plug-hole, holding it so that it rests on the piston and is as nearly as possible vertical. Make a mark-coinciding with some part of the cylinder head, to denote "t.d.c.". Then make another mark 7\16 in. above the first and turn the engine backwards until the marks on the stick show that the piston is 7\16 in. before the top of its stroke. Next rotate the contact-breaker until the points are just starting to separate and set the timing in the manner described in the preceding paragraph. If it is found that the stick cannot be held sufficiently upright for a reasonably accurate measurement to be made, it may be desirable to remove the cylinder head, assuming that it is detachable, but this is seldom essential. Always check the timing after resetting it, since sometimes it will slip during the tightening-up process. If it is dark and therefore the points cannot be seen properly, turn the contact-breaker until it comes up against the resistance of the cam; this can be felt quite easily and shows that the points are just starting to open. Then tap the sprocket on to its taper. Incidentally, with an electrically-equipped machine, the rear-lamp holder can be detached and used as an inspection lamp; it will light all right so long as its body is pressed against some metal part of the machine.

[a10 gf]

CHAPTER XIII IGNITION II

General Overheating
328. If a magneto runs hot, perhaps so hot that the varnish round the windings starts to melt the usual cause is that the armature bearings have worn to such an extent that the armature fouls the pole shoes.

Protection
329. On some machines the magneto is fitted low down in front of the engine where it is exposed to mud and water. In such cases either a tin shield should be rigged up or the magneto should be enclosed in an oiled silk sponge-bag. If the latter scheme is adopted, arrange the mouth of the bag at the rear of the magneto, or at all events in such a position that the mouth can be left partly open without fear of water finding its way inside. Should the bag be sealed right up and there be no air vent, a certain amount of highly undesirable condensation will occur.

Waterlogged Magneto
330. If a magneto appears to have become water-logged, first wipe the h. t. lead dry with a piece of rag or a handkerchief, and wipe away all moisture that there may be around the brush-holder; also see that the h.t. cable is clear of all metal parts of the machine. It is more than probable that attention to these points will cure the trouble, for with modern magnetos there is little or no chance of water entering the armature tunnel and earthing the slip-ring. If this does occur, and the trouble is experienced on the road, the only thing (assuming wiping the slip ring does not effect a cure) is to find shelter and dry out the magneto either by dismantling the instrument (see Paragraph 322) and drying it carefully with rag or by placing it in an oven, which must not be so hot that there is the possibility of the shellac-varnish on the armature windings being affected.

Villiers Flywheel Magneto
331. When dismantling the flywheel magneto on a Villiers engine, the following procedure should be adopted. The securing nut, which has a right-hand thread, is unscrewed in an anti-clockwise direction, looking at the face of the flywheel. The special spanner should be placed on the nut and hammered round in that direction. After about two turns it will be found to tighten; this is because the flange is pulling against the face of the flywheel. If a piece of wood is now placed against the face of the nut and hit sharply with a hammer it will loosen the flywheel on the taper of the shaft, and the nut can be unscrewed with the fingers till the flywheel is completely freed. When the flywheel is off, a piece of iron should be placed across the two pole shoes to prevent loss of the magneto flux.

Twin-Cylinder Magnetos
332. See that the two cams on the contact-breaker are of equal height, as shown by measuring the gap between the platinum points at each "break" by means of a feeler gauge. If the gaps differ, get them both to the exact distance recommended by the makers and shown by the feeler gauge on their special spanner. To do this, remove the cams from the timing ring and pack them up with paper washers.

Using Twin-Cylinder Magneto on a Single
333. It is possible to use a twin-cylinder magneto on a single-cylinder machine. The simplest method of utilizing one spark in the case of a twin-cylinder magneto is to earth one of the high-tension leads by attaching it to the frame of the magneto or the machine, thus allowing the high-tension current to escape without in any way damaging the windings. Another method is to extend one of the existing cams about half-way round the cam ring, so that during half a revolution of the armature the platinum points are held apart, with the result that no current flows in the primary circuit. In this case the high-tension brush that is no longer used can be removed.

Some Minor Points about Magnetos
334. Single-cylinder magnetos are designed to give their most efficient spark at full advance. Magneto chains should be inspected periodically, and, if necessary, adjusted, for any slackness will mean retarded ignition. The voltage of a magneto is something like 6,000 to 8,000, while the secondary current is only a fraction of an ampere; in the primary winding it may be 6 amperes. There are 8,000 to 10,000 turns of enamelled wire on a magneto armature.

Coil Ignition
Care of Battery
335. Current for coil ignition is supplied from the battery, on which, therefore, especial care must be bestowed when the ignition is of this type (see Paragraphs 148-169). Except when the engine is running slowly the ammeter will not show the full discharge which takes place through the coil and the contact-breaker. This is owing to the intermittent flow of the current and the fact that the instrument is not quite sensitive enough.

Battery Failure
336. If the accumulator becomes totally discharged on a machine fitted with coil ignition, the engine can usually be started up by connecting the battery leads to an ordinary flashlamp dry battery, or even the batteries used for electric bells. The battery (or batteries) should then be removed, when the engine will continue to run if the revs. are kept up, the current required by the coil being supplied direct from the dynamo.

Protection
337. The coil should never be mounted in an exposed position where water may reach it and cause a short-circuit. One of the best places for it is on the seat tube immediately beneath the saddle. If, however. the coil is incorporated in the dynamo, as is the case with some old machines, see that it is turned round so as to face to the rear. Should the machine be a multi-cylinder, there is, of course, a distributor which, if at all exposed, should be provided with some form of tin shield. Naturally the edges of the tin must be turned over so that the h. t. cables cannot be chafed through.

The Ignition Tell-Tale
338. When the ignition is switched on, the current from the battery can flow either through the contact- breaker and coil (unless the points happen to be open), or through the dynamo windings, in both cases returning via the" earth" to the battery, thus causing a steady discharge. Some warning is therefore necessary that the ignition is "on", and this usually takes the form of a red light in parallel with the dynamo windings and the cut-out, which lights up when the switch is turned "on". As soon as the engine is started and the dynamo commences to generate sufficient voltage, the dynamo current begins to oppose the battery current, till the cut-out (see Paragraph 188) cuts in and the contacts close. The dynamo current then takes the easiest path to the battery via the cut-out, neglecting the more difficult path through the red lamp, which consequently goes out, till the speed falls sufficiently for the cut-out to come into operation once more, when the lamp again gives warning that a discharge is taking place.

Sparking Plugs
339. Plugs are classified according to how much heat and how much oil they will stand. A plug capable of working under very hot conditions will stand extremely little oil, and vice-versa; this is why a racing engine is so often warmed up on a touring plug, which is replaced with a hot-stuff one just before the race starts.

340. A plug intended for use in a touring type of engine does not have to withstand very great heat, and, since the combustion head on this type of engine is often inclined to be "oily", the central electrode of the plug is generally thin, and composed of nickel or some similar metal of poor heat-conductivity; thus, by remaining at a fairly high temperature, it will prevent the deposit of soot or oil.
However, the plug in a high-efficiency engine has to withstand considerable heat, and for this reason is usually provided with very thick electrodes which can conduct away the heat and thus prevent any possibility of pre-ignition owing to the points becoming incandescent. Copper, being an excellent conductor of heat, is often used in connection with the central electrode of plugs of this type. The main disadvantage of the latter type of plug is that it is inclined to oil-up when the engine is "cold", but nowadays plug manufacturers can supply a compromise, i.e., a plug that will not oil-up over-easily when cold, yet will withstand a good deal of heat.

341. If pre-ignition is experienced with a new plug of the recommended type, and there is no question of the carburetter providing an unduly weak mixture, the plug manufacturers should be approached regarding a plug to suit the particular case. When the points of a plug burn away or "whisker ", the trouble is usually that the engine is too "hot" for that particular type of plug, unless some abnormal overheating due to some other cause has been taking place. Some racing magnetos also have had a tendency to "whisker" the plug; therefore if your machine is fitted with a magneto of this type and everything else appears to be in order, do not go bald-headed for the plug manufacturers but have a word with the makers of the magneto.

342. Continual oiling of plugs should be met by a change to a "softer" type, but first make sure that the gap on the type already in use is correctly adjusted (see Paragraph 349). If resetting the gap has not the desired effect, the use of a spark gap terminal, or one of the special "spark intensifiers" will quite probably overcome the difficulty.

Testing
343. With a multi-cylinder engine a plug, assuming the magneto is all right, can be tested either by means of a Neon spark tester, or by means of a wooden-handled screwdriver. Start up the engine and hold the screwdriver so that the blade rests against, say, the cylinder head or rocker box and comes within 1\16 in. to 1\8 in. of the plug terminal. If the plug is in order, a regular spark will occur between the screwdriver blade and the plug terminal. Naturally for this a screwdriver with an all-wood handle -one that is clean and dry- is necessary.

344. Another method of testing, which is the one usually adopted in the case of single-cylinder engines, is to remove the plug, rest it so that while its body makes contact with some metal part of the machine the terminal end is well clear, and kick the engine over. If the plug is firing properly, there will be a regular spark at the points. If there is no spark, or only a spark up inside the plug, there are three possibilities: (I) the insulation has broken down (which spells replacement); (2) the plug requires cleaning (see Paragraphs 347. 348); or (3) the gap at the points is incorrect (see Paragraph 349).

345. When using a Neon tube spark test, run the engine slowly and hold the business end of the tester on the plug terminal. It is probable that unless the plug is absolutely "dead ", some sort of a flash will be seen. If the plug is really working correctly a good bright flash should be evident. A dim flash will indicate that the plug is dirty or that the points are too close, and an irregular flash will indicate that the plug is sparking intermittently owing either to faulty insulation or to a film of soot or oil causing a short circuit. A Neon tester is particularly useful with a 4-cylinder engine as a rapid means of diagnosis, but it will be understood that a certain amount of common sense must be exercised in reading its indications.

Failure under Compression
346. A sparking plug will sometimes spark quite satisfactorily in the open air yet will not fire regularly under compression. The reason for this may be soot on the internal insulation, this soot, under these conditions, offering an easier path for the high tension current than the gap between the plug points. In such a case, it is very difficult indeed to detect the fault. If one adopts the wise practice of carrying a spare plug that is known to be in first-class condition and this plug is tried and proves to be perfectly satisfactory, there is a very strong clue as to the cause of the trouble. The gap should be checked (see Paragraph 349) and if this is in order, the plug carefully cleaned in accordance with the hints that follow.

Cleaning
347. Much can be done in the way of cleaning the electrodes and body of a sooty plug by careful scraping with an old penknife, that is, once the plug has been "split ". Most plugs are of the detachable type and can be dismantled quite easily if care is taken-or ruined if the job is tackled haphazardly. Mount the hexagonal body of the plug in a vice and then instead of using an adjustable spanner or an ordinary set spanner on the somewhat flimsy gland nut, employ either a ring spanner or a box spanner -one that fits the nut perfectly. A ring spanner is best because a box spanner is rocked rather too easily. A few taps on the end of the ring spanner will generally do the trick.

348. For cleaning the insulation of the plug, a piece of coarse rag, benzole mixture; and hard work are about as good as anything. Some people use emery cloth, which is quick but damages the insulation and sometime,s makes it rather too liable to sooting up. Other folk use caustic soda solution for cleaning plugs-in the same manner as used for engine decarbonization -but this spells ruination to some plugs.

General
Plug Points
349. As a rule the points of a sparking plug are adjusted by bending the point or points on the plug body until there is the required distance, measured by feeler gauge, between them and the central electrode; in no circumstances should the central electrode be bent. It frequently happens, however, that with detachable plugs the plug centre is slightly eccentric, and can be moved round as regards the plug body until the correct gap is obtained. The usual gap is 18 to 25/1,000 ths in.

350. After long usage, sparking-plug points burn away; the gap should, therefore, be tested periodically.

351. Black soot on the plug points denotes too rich a mixture. A weak mixture is denoted by a hard whitish appearance.

352. A sparking plug that is faulty can often be made like new by its makers at a cost considerably below that of a replacement.

353. A heap of old plugs lying about in any sort of repair is not much use. They should be properly cleaned and tested, and consigned to the dustbin if proved faulty and not worthy of renovation.

354. A square of patching rubber with a hole in the centre may be slid on the high-tension cable so that it is just in front of the plug, to provide an efficient substitute for a plug protector in cases where this useful accessory is not available.

355. When the terminal nut or clip has been lost, the h.t. cable may be kept on the plug by twisting it round and round a few times, like model-aeroplane elastic, before hooking it to the terminal; the natural "untwisting" desire of the cable will prevent it from coming off under all normal conditions.

[a10 gf]

"A somewhat exciting but certainly the quickest way of finding out whether the magneto is functioning is to place one finger on the plug terminal and at the same time kick the engine over"

lol

[madsens]

Tried that... or kind off 

Cleaned the slipring with a rag on a finger - that was before I knew very much about how a magnet works - and it did work! glad I didn't use a pacemaker....

regards
Joergen