Magneto issues

[BSA500]

Well after completing a winter rebuild that started with a rattle and burning oil turned into shot small ends, replacing the pistons/rings and reseating all the valves etc etc I started her up. I found the old problem of difficult to start and unpredictable running was still there (was sort of hoping running on 50:50 oil/petrol was the main reason ). The sparks come and go and dont look brilliant. No problem say I just send it off. Big problem it seems everyone is rammed with jobs looking at between 2-4 months waiting lists on jobs.
 So my question is with those symptoms is it worth trying the easycap seeing as it was rebuilt 7 years ago by Priory mags and has a good slip ring brushes points bearing etc etc

[groily]

It's impossible to be dogmatic but if it's hot starting and running that's the problem, then that might point to a condenser problem. (Or, mind, to a coil, slipring, pick-up, contact-breaker / camring one.) 
Absent being able to test the condenser (which is hard to do in situ) your best bet has to be to talk nicely to Andrew at Priory I reckon. There's probably 'nothing much' up as it's one of his, but it's hard to know and a fair bit can certainly happen in 7 years because 'things do'. Chances are the coil's good, you say the rest of it's good too, but looks can be deceptive.

Of course, with a vested interest of my own I'd be very happy for you to buy an Easycap - but not if the result is no improvement after the work of fitting the thing: I hate it when that happens.

There are various tests you can carry out on your own though - including:
check the HT coil's simple resistance from slipring brass to earth/ mag body (c 5000 ohms). Open Line is bad and 'Help Needed'
check the HT pick-ups are undamaged
check the brushes move freely and if you have replaced them since the rebuild check they haven't made black dust tracks round the slipring (guaranteed misfiring)
check the HT leads from plug cap to brush for continuity (very low ohms - best to use non-resistor plug caps)
try other spark plugs
clean the contact breaker and check for sensible gaps on both cylinders (and if it's a steel backplate make sure the spring on the opening point isn't kissing the camring)
etc.

Valve clearances and carburation plus ignition timing + ATD if fitted are presumably OK after all the things you've done.

[BSA500]

Thank you for the answer very helpful. I would ask Andrew he is very helpful but I can see like many in his trade he is very very busy.
 In answer to some of the questions. Plug caps are nonresistor type. I stopped back the htleads to rule them out anyhow,when the sparks stopped they stopped on both leads at the same time.suggesting the fault lays inside the mag. No tracks on the slip ring and I use the brushes supplied by Andrew. Brass points spring not touching. Rest all gaps plugs points etc and reset timing.

[groily]

Is it a 'when it's hot' thing, or an 'always' problem? Hot is usually related to condenser, coil or failing plastic bits, but will often start as random misfiring rather than total loss of both sparks. Total loss, but intermittently and from cold, is a bit rarer I'd say, but can't rule anything out on those grounds alone.

I really would check the resistance of the HT winding from the slipring brass segment to the mag body, and I'd also physically check the earth brush, especially if you have a fibre pinion drive, which won't provide a return path for the HT current if the brush isn't doing its job. (If your contact breaker has an auxiliary earth brush on its rear face, an earth problem is less likely though.)
No continuity across the coil says one of three things is happening:
bad ££ = a break in the winding (unlikely);
semi-bad ££ = poor connection of HT coil to slipring (not very likely);
hardly any ££ = intermittent or no earth.

You might also take your meter to the cb end, and with the cb still attached measure the resistance across the points when they are open - when you should see half an ohm, which is the resistance of the low tension winding.. Shut, you should ideally see zero. Many meters aren't too good at very low levels though, so the difference shown might be a bit hit and miss.
If you take the cb unit off, and measure across the points, open, there should be no continuity. If there is, then look at the thin insulator plate and the tophat tubular insulator that are under the fixed point brass block (or bits of bent tin on steel cb units). If yours is steel, be 100% sure the opening point spring absolutely can't touch the camring as I mentioned before - it's live on them and a kiss is fatal to the spark. Closed, across the points, cb unit off the mag, you want your zero ohms again, or near as.

If the resistance readings and the earth brush are all in order, then there's not a lot more you can do than you already have without taking the mag off again.
If you had it off again, then you could certainly TRY a condenser on the points if you could get at and snip the low tension live wire at the condenser end to disable the one that's in there. Nothing much to lose anyway! But having got that far, you'd probably want to be sure all elements were still good and to spec, which means coil testing hot and cold and ditto for the plastic parts.
The Lucas workshop instructions for various mags provide decent info on how to test a coil (same for all pretty much) if you could be bothered to create the test rig, but otherwise it's easier to ask someone with the kit already to hand.

[BSA500]

Thanks Groily all very useful stuff.
 The main symptoms are very difficult start from any temp 5/6 kicks, if you keep the revs up its ok but if you let her come down to any sort of normal sort of tickover she will spit and die. I know people will scream carb but no that has been resleeved/ jetted/faced in excellent condition. The typical example was the other day has finished rebuild run her up a couple times and decided to run her around the block. Kitted up rolled her out, consider I had started her up ten minutes before, kick kick kick etc etc etc nothing at all, pulled the leads, bared the wires(excluding plugs and caps) no sparks. 2 minutes later intermittent sparks, 2 more minutes ok sparks a little 'white' not blue if that helps.
 I am poking the mag tonight while the wife watches the soaps, I need to get out I'm depressed enough

[BSA500]

Last year was a typical failure, half way to work, 13 mile journey pulled up to a junction, bike just died. Would not start for a couple of hours, when it did it ran like a bucket of bolts next day seemed fine but all this time still taking lots of kicks to start etc

[berger]

i have not been to the pub but having read about maggy plugs to stop the timing slipping a degree or two i was pondering and bored so i made one , i may well use it on the berglar build . the pluggy thing has been cut down and tried in a maggy and it works , so PUB tomorrow 

[RichardL]

Well, I'm a slow reader, so, while Groily is cautiously avoiding self-promotion, and 500 describes the unfortunate troubles, I think I could have had my mag mostly off and halfway to an EasyCap fitting (if I didn't already have one). Throw in the combined time it took to write this and their posts, and it's probably ready to be reinstalled. I say, if the mag is coming off again, just do it. Even if it is not the key cause of the trouble, it represents an improvement and protection against a possible (maybe, likely) upcoming cap failure. If you, 500, haven't already watched the EasyCap bench-test videos I'm sure you will find them interesting.

Richard L.

[BSA500]

Well, I'm a slow reader, so, while Groily is cautiously avoiding self-promotion, and 500 describes the unfortunate troubles, I think I could have had my mag mostly off and halfway to an EasyCap fitting (if I didn't already have one). Throw in the combined time it took to write this and their posts, and it's probably ready to be reinstalled. I say, if the mag is coming off again, just do it. Even if it is not the key cause of the trouble, it represents an improvement and protection against a possible (maybe, likely) upcoming cap failure. If you, 500, haven't already watched the EasyCap bench-test videos I'm sure you will find them interesting.

Richard L.

i am 90% there don't worry but I will do the checks esp the HT coil because God hates me and wants me to spend extra money and time. Also I want to check I haven't had a senior moment some where. 

[RichardL]

Yes, I did mean to mention following Groily's testing procedures, but that's obvious, anyway. Hoping for a quick, satisfying, result for you.

Richard L.

[groily]

Last year was a typical failure, half way to work, 13 mile journey pulled up to a junction, bike just died. Would not start for a couple of hours, when it did it ran like a bucket of bolts next day seemed fine but all this time still taking lots of kicks to start etc

Hmm - that does sound like possible condenser trouble, have to say. On the classic side of typical even.
That's pretty much exactly how the last internal condenser I had, in an exchange armature from SRM on my A10, died at very low mileage. That was after endless starting trouble which I understandably put to down to everything else first.
Annoyed me so much that I started trying to figure how else the job could be done so I would never again have to take off a mag, strip it and reassemble and retime the engine for the sake of one of the cheapest bits on the bike. Which, with the refinements and design skills of my late engineer-guru and patent attorney mate KenF who used to post on here too, we turned into a sellable gizmo. A prototype did best part of the 50+K miles I did on the A while I had it, and is still on there. My very oldest one, at nearly 12 years is on an AMC 500 twin; newer ones are on my three other twins and also lawn mowers, and anything else with an old-fashioned engine, with mags, battery/coil or flywheel mag ignition. I think there are now over 25,000 of them out there, but we stopped counting long ago.
End of sales patter/shit.
If it is a condenser problem, seems as if it could be worth a go.

[BSA500]

Wel if I did this right it looks like the HT side is fubar .Had to take it off the bike first it was such a faff on the bike. Set the meter to 20000 ohms or 2000 nearest to 5000 my meter had. With the probes apart display showed 1.Connected one to the mag mounting hole and touched the brass segment no change on the meter all the other tests were fine. Bugger. As I said before the issue is that everyone is stacked with work

[groily]

Is there continuity (close to zero ohms) between the mag body and the armature spindle? Should be, if the earth brush is good.

If there's infinite or mega-ohms from brass on slipring to spindle (or body if brush is good) then  there's a break in the winding, the slipring isn't making a connection where it attaches to the coil or the low tension earth wire has come adrift at the condenser end. (The latter not likely if you are getting correct readings at the contact breaker though.)

If the mag's off the bike, you might as well take the armature out - the magnetism won't run away - have a look for anything obvious and measure slip ring to spindle again. Just remember to take out the safety gap screws that point at the slipring from the outside, or you'll damage the flanges on it.

If you could get the bearing race outboard the slipring off without busting anything, you could hoick the ring and measure direct from the spike off the coil to the spindle to see if the problem is a bad connection there. If still an open line / infinite reading across the coil, there's a break in the winding.

Doesn't sound too promising if your tests so far are right, but don't despair, everything is fixable.
How soon do you need the thing running again?

[BSA500]

Again thanks for the reply and test suggestions I shall try them when I get home from work. Out of curiosity I popped the armature out of the mag this morning. Nothing looks amiss (who am l kidding how would I know ). I can see the capacitor, flat brown two small thin wires, but there are two thick red wires one either side of the coil twisted together covered in paint? Seem to both connected to the capacitor difficult to see,I will try to take a pic.
With the bearing removal does the ball race just roll off with light finger pressure the extractor needed fir the inner race and slip ring.
Ad for when I need it for I was sort of hoping to be riding it by now lol

[groily]

A pic would be good but there will be 2 wires off the coil, one each side, the live and earth low tension leads.
The live one will be a double-strand within the insulation, as one strand then goes (from where it joins the condenser) to the contact breaker end through a groove in the bobbin, arriving at the bent tin tag that the cb centre screw attaches to.
The earth wire usually joins one side of the condenser (the wire off the coil will be single strand under the sheathing) and then the joined wires will go to earth.

The bearing cage and balls just slip off with gentle levering - but the race is a tight fit and needs an extractor. Not sure if there is a commercially-available tool out there at a reasonable price, and as there's no room behind the race to get a knife-puller on, it can be a bit of a PITA.
You hear of people using a thick single strand of copper wire in the ball groove and holding the race in a vice using the wire as a protector, then tapping the spindle - but it's not great practice and could crack the race - they're brittle obviously. A steel plate drilled to just go over the race, with grub screws threaded in from the edges to engage the track for the balls can be good though (used with a suitable legged puller), otherwise it's a 'profile' clamping tool that fits the bearing race properly.

Sliprings usually come off with firm but steady hand power, they are rarely difficult, especially when they've been replaced in the not so distant past.

Even if there is no HT continuity from slipring to spindle, you can check the coil is earthed by putting a meter across from the cb centre screw to the spindle - you should see half an ohm there. (The earth for the low tension and HT windings is common.)

But no point driving yourself nuts trying to get the slipring off if it's hard - you're in 'help' territory anyway by this time if there's no HT circuit. Even if you did get it off and the fault was there rather than inside the coil,  you'd not be out of the woods necessarily owing to the possible need to play with the shimming behind the race to adjust end-float on reassembly. 

If you were nearer you could borrow a spare mag or an armature and we'd sort this one in short order because I'm retired and have time on my hands - but it's a bit hard from here!