Author Topic: Lining up the Timing wheels... What should I do?  (Read 5898 times)

Online groily

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Re: Lining up the Timing wheels... What should I do?
« Reply #15 on: 17.09. 2009 22:24 »
Can't have everything . . . the cam pinion teeth will indeed always be loaded at the same points - as the lobes whack the followers. But if the idler teeth which bear on the cam pinion are constantly changing because of the idler's funny size, then the overall wear on the gear train will be much less than if it was the same idler tooth contacting the same cam pinion tooth every time for each follower. That's the theory anyway. BSA, Triumph and AMC twins followed the same practice in their different ways, successfully I'd say. Norton and Royal Enfield twins of the same era preferred chains for their single and twin camshafts respectively (hence their clockwise rotating magnetos - no reversal of direction en route).
Not sure whether chains/sprockets suffer from localised wear or not (suppose they must to some extent), but they are certainly more of a pain to set up than a gear train, there are 2 of them (one for the mag/distributor/whatever), and then they need periodic maintenance as well to keep them tensioned. And that's without thinking of how to turn the dynamo, if there is one.
Cars are pretty much the same: setting chain driven twin ohc engines is a fiddle; gear driven is in principle a lot simpler - although as anyone will know who's played with a set of helical timing gears, they can be a fiddle too.

And while we're on, why did only AMC have the wit to use steel mag pinions? I have now seen no fewer than 4 fibre mag pinions fail in the last 18 months or so: my A, a Sprung Hub Speed Twin, a Vincent Twin and a Venom. That's a high rate of attrition, albeit on some very well-used bikes. The A and a local friend's Speed Twin now have alloy gears. Now, right back on point, they probably DO need swapping around on their shafts from time to time to even out the wear!



Bill

Offline Tone

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Re: Lining up the Timing wheels... What should I do?
« Reply #16 on: 20.09. 2009 18:14 »
You lot have got me a bit baffled, not hard, I've had my idler pinion off, forgot and turned the engine over while doing something on the clutch, do I move the engine around until I can slot the idler pinion in with the Marks lined up, or do you have to have the engine in any particular position? I think you must do otherwise wouldn't the pistons be in the wrong position to the camshaft???

Online bsa-bill

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Re: Lining up the Timing wheels... What should I do?
« Reply #17 on: 20.09. 2009 18:45 »
Yes turn everything around until marks line up and slide idler pinion in to align marks, this is the safe way.
If nothing else had moved ( crank or camshaft ) you could just slide the idler pinion in but can you be sure???
IIRC with marks lined up engine is at TDC

All the best - Bill
All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco

Offline A10Boy

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Re: Lining up the Timing wheels... What should I do?
« Reply #18 on: 20.09. 2009 18:52 »
Tone, The answer is both.

To avoid a valve / piston interface situation, take out the plugs and carefully set the pistons at the bottom of their stroke. Then turn the camshaft until the dot points to the center of the idler, then turn the crankshaft so the pinion dot is also towards the center of the idler pinion. Then slot the idler back in position with the marks correctly lined up.
Regards

Andy

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Offline LJ.

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Re: Lining up the Timing wheels... What should I do?
« Reply #19 on: 20.09. 2009 19:01 »
Tone, The answer is both.

To avoid a valve / piston interface situation, take out the plugs and carefully set the pistons at the bottom of their stroke. Then turn the camshaft until the dot points to the center of the idler, then turn the crankshaft so the pinion dot is also towards the center of the idler pinion. Then slot the idler back in position with the marks correctly lined up.

That's a good answer which I did not know. Would Tone also then have to re time his magneto? or would that still be correctly timed? Probably a good idea to re check it of course.
Ride Safely Lads! LJ.
**********************
1940 BSA M20 500cc Girder/Rigid- (SOLD)
1947 BSA M21 600cc Girder/Rigid-Green
1949 BSA A7   500cc Girder/Plunger Star Twin-(SOLD)
1953 BSA B33  500cc Teles/Plunger-Maroon
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1961 BSA A10  650cc Golden Flash-Red

Offline A10Boy

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Re: Lining up the Timing wheels... What should I do?
« Reply #20 on: 20.09. 2009 19:17 »
No he wouldn't as the camshaft and mag haven't been separated.
Regards

Andy

1960 A10 - Black Golden Flash
Plus
1974 Kawasaki Z1a
Yam XJR 1300