A7 Longstroke Lubrication

[Swarfcut]

 With member Brandis asking the Longstoke questions, I've been looking a bit closer at my Longstroke project, and racking by brains on why the cam wear was so bad. Some folks have all the luck, but mine has had a raw deal.

 I compared the crankcases with later shortstroke types, and there are a few things that seem strange. The history of this Longstroke motor is unknown. I also have another scrap Longstroke crankcase, and it is the same. Both from August/September 1949, the traditional Factory Holiday shut down time of the year. Maybe that's the answer.

   I found that on both crankcases the three camshaft bushes, together with both idler shaft bushes, have no provision for lubrication directly and no oilway scrolls cut into the bearing surface. The crankcase castings have all the oil holes drilled as usual, but the cam bushes themselves have never had an oil drilling. Same for the idler shaft, both bushes plain and undrilled. Later engines have the drillings in the bushes to match the castings and the back to back scroll oilways in the idler shaft bushes.

 Could be mine was a Friday Afternoon Jobbie, but it would be interesting to compare what other folks have.

 All the oil from the rockers is fed back down the pushrod tunnel. There is no oilway from the exhaust valve spring pockets  back to the crankcase as on the shortstroke. At the bottom of the pushrod tunnel oil can find an easy path to the flywheel via the narrow gap between the tappet retaining plate and the bottom of the barrel flange. Direct feed to the cam is by any oil passing down the followers, oil mist and good luck. Not what we really want. There are drillings in the centre tappet block, but none lead directly to the cam lobes, but feed the follower shafts and the rear face of the followers.

 Swarfy.

[Brandis]

So, in 1947 #280, which is probably among the earliest ones in the Forum . . .
- After 12K on the odometer, very little wear on the far end of the camshaft.
- the far end bush has a 'swirl' cut in the inner diameter connected to the drilled hole.
- hole is drilled to a tiny shelf in the casting which catches random spray and stuff coming down the intake push rod.
I assumed most A7s were like that.

The journal next to the gear shows no visible wear.  For a bike with that mileage, it looked pretty normal.

I assume that the serious flaw that plagued the first 500 was not in the camshaft and it had not been removed when the crank was removed.

[Brandis]

So I'm down to deciding on whether and where to drill extra 1/16" oil holes in the crankshaft and the old steel conrod.  I recall that RDFella pointed out that the rear of the piston/cylinder interface had more stress because when the cylinder fires, the big end swings forward and the reaction force at the little end pushes the piston to the rear of the cylinder. So a squirt of oil from the 10:00 o'clock position on the rod, giving a squirt in the way up?  Or is the quality of oil better now so the old oil system will do alright?
It's Saturday night.  Perhaps I'll drink some more beer and watch old episodes of The Saint.  Then decide in the morning before the England match.
By the way, the best place to get really difficult A7 parts is Mike's Classic Cycle in Brisbane, Oz. No matter how obscure my request, he's got it at a price that can't be beat.

[Brandis]

So, having a very early unit with known lube problems, I tend to be a bit paranoid on the subject.  The oil feed line to the rockers simple tees off the oil return at the tank  I assume this because I've never seen a working A7 or A10.  It doesn't seem like it would be sufficient. 
My engine came apart after 12K miles and was put in storage about 60 years ago.  That mileage was sufficient to have the first owner pull out all the valves and an exhaust guide. I hate to put it back as it was.  Should I be thinking of finding a pressure source to feed the valves?

[Swarfcut]

 Author Roy Bacon cites no feed to the rockers on early engines, then to the exhaust only for 1947, then to both exhaust and inlet from 1949. Feed to the rockers via a T from the return line is the standard layout on all later engines and works well, the Achilles Heel being the banjo bolts  on the rocker box. Early engines used 65 306, from 1954 it's 65 317. My assumption is that the only difference is the size of the hole, which in effect acts as a crude metering arrangement. Other ranges used similar basic parts, but fitting the wrong ones alters the balance of oil heading to the rockers. Plenty on the Forum, a good few over oiling problems are down to the wrong bits and maybe an answer lies in Julian's archives.

 Rocker shafts on early pre XA7 450 are 67 59, which presumably are solid, with no central oilway. Later Longstroke engines with rocker feed use the same centre oilway shaft  as later engines, 67 64, so later drilled shafts should be a straight swap to add rocker lubrication to an early engine, along with later banjo feed pipe, bolts and  a T from the return line.

 Looks like we're holding back on advising the wisdom of drilling holes in conrods......

 Swarfy.

[Brandis]

Thanks, as always.  I'll file my concerns under oiling paranoia.

Now it's on to my speedo which, after more than half a century, is seized.  Just getting the case open seems to be the trick.  I'm sure the Forum has some info.

[Greybeard]

Thanks, as always.  I'll file my concerns under oiling paranoia.

Now it's on to my speedo which, after more than half a century, is seized.  Just getting the case open seems to be the trick.  I'm sure the Forum has some info.

This is off topic but, I soaked the threads in penetrating oil for months while I got on with other jobs on the bike. I needed to warm the case before I got the bezel turning.

[Swarfcut]

 Once that bezel comes off you are faced with one of the most fiendish examples of the clockmakers' art. A Chronometric is just that, delicate and made with the precision of a watch. Leave well alone and consign to an expert. Even scrap ones have an astromical value only dreamed of by the makers. A restored example will cost a lot.

 If you are determined, the bezel has a normal lefty loosey thread. A couple of strap wrenches, lubricant and gentle heat from a hot air gun should get it to move. My advice.....see above.

 Swarfy.

[Brandis]

Swarfy:
Off topic, but we talked about measuring end play on the A7 crankshaft.  But the interference fit on the roller bearing is VERY tight both on the shaft and into the casing.  The idea that I could spin the freshly installed crank, put a machinists dial gauge on it and ease it left to right to measure the drift, is pure fantasy.  When it goes together it will be where it is and I will have to assume it will be OK.

PS:  I decided to drill holes in the con rods to put a little extra oil onto the flywheel and hope enough gets up into the rings.  It was kind of a flip-the-coin engineering decision based mostly on how bad could it be.  Not very professional.

[RDfella]

But the interference fit on the roller bearing is VERY tight both on the shaft and into the casing.

There is no engineering reason why the inner race needs to be a tight press fit on the shaft. A push fit will be just fine, so ease the shaft it it's too tight. Of course the outer race needs to be an interference fit in the cases (my preference is .004" to .005"). A standard roller brg is not appropriate in these circumstances: an extra clearance brg is required - at least C3 (I prefer C5). In that case, the brg will still move. If it doesn't, it'll overheat.

[Brandis]

Makes sense.  The crankcase will expand more than the crankcase when it heats,  so there's got to be some give. I bought the bearing from Draganfly, so I assume it is correct. 
I'll 'ease the crank diameter and follow the proper drift measurement technique.  I have shims on standby.
Thanks, as always.

[Swarfcut]

  Brandis.   The early A7 engines use a ball race on the drive side. In this case the whole of the bearing stays in the crankcase, the crank being a theoretical "tap it out gently with a hammer fit" rather than with a 10 Ton Press. As RD says, there is no need for these tight fits on the crank, the cush nut pushes on the drive sleeve, which in turn pushes and clamps the bearing inner race against the crank. The only float will be that within the ball race, in other words zilch. With a ball race, how you establish the running clearance against the timing bush requires a degree of movement between the crank and inner race, or a feeler gauge that goes round corners.... my guess is folks just don't bother.

 The later engines use the demountable roller bearing and again there is enough on the forum about press fits, push fits, Loctite and hammered nuts. The basic premise is the end float is determined by the circular shims between the inner race and the crank, and the big nut tightened down as before.  Early engines with duplex chain use a different cush sleeve and nut from later S/A motors.

 I suppose a roller type bearing would fit your early cases, in which scenario follow the established procedure for setting the endfloat on later engines. For a low stressed engine a ball race would seem to be a cheaper and more straightforward option, some Forum Members have done this with the later engines.

 In his book, David Munro indicates the A7 used a ball race for all years and models. Clearly this is an error.

 Swarfy

[muskrat]

G'day Brandis.
The reasoning behind crank end float is that with nil and it's all cold the crank could be clamped so the 2-3 thou lets the crank spin. If the endfloat is greater than this when hot the gap grows and oil pressure will be lost between the bush thrust face and crank web.

If I were to do a long stroke I'd install the bearing and cush components into the drive side case. Then put a strip of plastigage on the crank web and lower the timing side case onto the crank and tighten all the bolts/nuts. Then remove the case and measure the plastigage strip.
A bit of a process but not that far removed from doing the endfloat of a short stroke. https://www.plastigaugeusa.com/how.html
Cheers