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Timing gear whine
#802469 03/23/20 5:12 pm
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I just finished restoring a 1972 BSA 750 Lightning, A70L. Basically the same bottom end as a A65L.

The timing gears are making a loud whining noise. Louder than I remember hearing from a BSA twin before. Am I remembering wrong? are the timing gears normally loud on these or should I be concerned?

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Re: Timing gear whine
BritBoy #802474 03/23/20 5:32 pm
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Can't help with BSAs, but loud whines are usually heard from Harley owners getting their repair bills.

Re: Timing gear whine
BritBoy #802476 03/23/20 5:36 pm
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Gears in tight mesh ?, should be some slight backlash.

Re: Timing gear whine
BritBoy #802485 03/23/20 6:09 pm
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When you "restored it", what did you actually do?

Re: Timing gear whine
BritBoy #802486 03/23/20 6:10 pm
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Worn intermediate gear bush either in the timing cover or case will cause a whine. Misaligned bushes on the intermediate gear will cause a similar noise.


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Re: Timing gear whine
BritBoy #802507 03/23/20 8:22 pm
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When I restored it I went through everything. The whole bike. I made sure everything was right when I put it back together but I guess I'll have to pull it apart and double check it all. Dang it!

Re: Timing gear whine
BritBoy #802511 03/23/20 8:31 pm
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Did you replace the idler gear bushes?

If so (and to further Rich’s comment) did you fit the inner timing case to the crank and run an 11/16” reamer, line reaming the two. If you haven’t... you may find that the bush will grip to the idler gear pin and spin the bush or bushes in the housing. If this is the case you’ll need a new idler gear pin as well as another set of bushes.


beerchug

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Re: Timing gear whine
BritBoy #802515 03/23/20 8:52 pm
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No I didn't replace the bushes. Unless I screwed up on my measuring they were good.

Two steps forward and three steps back. sounds like I need to go back in.

Re: Timing gear whine
BritBoy #802517 03/23/20 9:30 pm
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Replace the crank bush? With steel back or solid bronze? Ream afterward? Hard to make accurate guesses without knowing what changed.

Re: Timing gear whine
BritBoy #802522 03/23/20 10:05 pm
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Yes. replaced the crank bush with steel backed bush and reamed.

Re: Timing gear whine
BritBoy #802528 03/23/20 11:15 pm
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Because you want to prevent the "clicking" sound related to the valve springs alternatively changing the rotational pressure on the teeth you want nil clearance between the cam gear and the idler gear. You want .001 to .002" clearance between the idler and the crankshaft pinion gear. On you nil clearance you want to have the gears able to rotate with out any binding or clearance. If the cam wheel binds against the idler gear any place in the rotation they will most likely whine.


Re: Timing gear whine
BritBoy #802531 03/23/20 11:26 pm
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Ive changed timing gears in my A65 , been lucky no whine, whine is too tight somewhere, I have had whine from a too tight primary chain, never the timing gears, what normally comes from there is clatter, not much.
Its easy to over tighten the primary chain, judging slack is difficult, check when hot, if its like a bow string, back it off.
Or I am 100 % wrong, and it is some other weirdness , we can only guess at. Timing gears were originally matched to the engine, best fit from the boxes on hand. With tolerance stack up it might be possible to end up with a set on the plus side that make a noise, that would mean zero backlash on assembly, gears should mesh so that a piece of news paper passes through with no binding. Some of the gears tried were eccentric and meshed tight/ slack. they were rejected.

Last edited by gavin eisler; 03/23/20 11:38 pm.

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Re: Timing gear whine
BritBoy #802546 03/24/20 12:06 am
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Question: Are there serious implications to problems leading to timing gear whine in the long term? (I realize that this would depend on the degree of the problem.)


Mark Z

'65(lower)/'66(upper, wheels, front end, controls)/'67(seat, exhaust, fuel tank, headlamp)/'70(frame) A65 Bitsa.
Re: Timing gear whine
BritBoy #802550 03/24/20 12:37 am
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Probably, He is never going to stop whining about the engineering. Oops. Wrong thread ? Sorry, I couldn't help myself.

Re: Timing gear whine
Mark Z #802554 03/24/20 1:00 am
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Originally Posted by Mark Z
Question: Are there serious implications to problems leading to timing gear whine in the long term? (I realize that this would depend on the degree of the problem.)

Originally Posted by Tom A65LR
Probably, He is never going to stop whining about the engineering. Oops. Wrong thread ? Sorry, I couldn't help myself.

No, I'm serious and I have a reason for asking. My son is currently restoring/rebuilding an A65 and did replace idler pinion bushings, and possibly one or more timing gears. Engine has not yet been started.


Mark Z

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Re: Timing gear whine
BritBoy #802589 03/24/20 9:05 am
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The other reason they whine is the bush is not alighned properly or the case hardening has worn through or the teeth have worn out of profile.


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Re: Timing gear whine
BritBoy #802598 03/24/20 12:26 pm
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if idler gear is bushed make sure it has been bored(not reamed) Concentric to the OD of the gear.

Re: Timing gear whine
BritBoy #802620 03/24/20 4:12 pm
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This can be done in a lathe, at slow speeds. It's easy.

I saw my dad do this many times.

Re: Timing gear whine
BritBoy #802660 03/24/20 7:14 pm
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In my T100, when I had my intermediate shaft for the timing gear in the middle of the cluster re installed with a bush in the case ( by the local machine shop ) as the original had been put back in the engine after the outer half had broken off when the engine had hit the road in a spill and subsequently thrashed about, re installing the pinions didn't go easily so, like they apparently did on assembly in the old days at Triumph, I went through the pinions I had from other engines I had until I found a nice fit and that solved the problem in my case. Of course, I was glad I had bought up part engines at swap meets to have a selection of pinions to sort through and got lucky. Sometimes hoarding can be a good thing. Not so easy to find engines and parts these days it seems.

Cheers, Wilf


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Re: Timing gear whine
RGSROB #802738 03/25/20 7:42 am
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Originally Posted by RGSROB
if idler gear is bushed make sure it has been bored(not reamed) concentric to the OD of the gear.

I can understand why you say bored Concentric but I have in-line reamed several motors with zero problems. It is important though that you mount the inner and crankcase prior to reaming.


Edit: just to clarify as I think I have been confused by RGS ROBs comment, re-reading I think he is reffering to the pinion gear itself being bushed, I beleive the Triumph twin intemdiate gears are like this. my comment above is relative to the BSA unit twin which is a fixed pinion gear to pinion (shaft), the ends are supported by the bushes being into the case.

I'd be grateful if you could clarify further on your comment Rob, just to make sure we are not at crossed minds/topics on the subject.

Regards

Last edited by Allan Gill; 03/26/20 9:51 am. Reason: re-read the quoted item

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Re: Timing gear whine
BritBoy #802998 03/27/20 3:47 am
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It's an A70, just keep it over 5000rpm, you'll never hear the whine................................


Moderated by  Allan G, Jon W. Whitley 

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