Author Topic: Idler gear, dynamo drive etc  (Read 2648 times)

Online groily

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Idler gear, dynamo drive etc
« on: 04.10. 2007 12:52 »
In search of source of swooshy rattle am investigating dynamo drive and timing gears. In the outer case, chain very stretched, many rollers very stiff on their pins, and sprockets pretty worn. All scrap. At the same time, I noted that there was a lot of end-float on the drive sprocket/idler gear shaft. By a lot I mean a good 50 thou. I was also missing the cork or felt washer I seem to remember goes between the sprocket and the inner timing cover. That'll be rectified with a belt drive conversion which comes with missing washer etc - but a Q for those who know. Is it normal/does it matter to have that much float? How much ought there to be!? Will the missing cork washer take it up without self-destructing or would a wise man insert a hardened spacer on the idler shaft inboard of the gear itself to reduce it to something sensible (6-8 thou?)? I should add there is no appreciable wear on the outer idler bush, and I'm happy with that.
For those interested I've ordered the SRM toothed belt gubbins, which will give 10% increase in dynamo rpm in preparation for going 12 volt (with standard 6 volt-wound dynamo and 12v solid state box) when I get round to it. Not cheap, but looks a good bet and should last well (says he hopefully). Any views on any of this from you who know these bikes much better than I do? Groily
Bill

Offline dpaddock

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Re: Idler gear, dynamo drive etc
« Reply #1 on: 12.10. 2007 07:44 »
The cork washer goes between the dynamo end plate and the inner timing cover. I know this is shown differently in the spares book, where the washer is shown on the INSIDE of the cover, but the only way to seal the chain cavity is to place the washer on the outside.

End play at the drive sprocket indicates that the idler pinion spindle oil seal is missing or worn. The p/n is 67-708.

Re 12 V conversions, there's much to be done to prep the system and the results might not be worth the effort.
David
'57 Spitfire


Online groily

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Re: Idler gear, dynamo drive etc
« Reply #2 on: 12.10. 2007 11:01 »
Ta very muchly for the advice dp.
Installed the belt drive a few days ago, with new cork washer as wot was missing, and all seems very well. Difficult to do up the dynamo pulley properly in situ, as remarked elsewhere in relation to some belt drive conversions. No endfloat on the idler shaft with all assembled, but you're probably right about the seal etc although there's no oil in the compartment and the dynamo itself was clean as a whistle inside. Most noises, and certainly the horrible ones, have now gone - the rest can wait till the whole engine comes apart as it surely will in due course (if only to reassure me as to what's in there on what is clearly a mix of bits).
Have been running 12 volts on another twin for over 20 years and nary a prob . . . that uses an original JG box of tricks from the '80s, and neither it nor the dynamo - 6 volt wound - have given any trouble in frequent use.
IMHO for what little it's worth 6v-wound is better, even if you need more revs to get it to balance the draw on the battery, cos the wires are thicker - the 12 volt windings are very very fine, obviously. Mine's kept the battery up even when I used the thing as daily transport in London for years. That runs a 60-55 halogen h/light. Was thinking of doing the same thing with the A10 using the Podtronics 12 volt box for 6v wound dynamos. Don't anticipate any probs, but fate does lurk round corners with a brick sometimes. Reckon it'd be better for the slightly skimpy loom on the bike too - I'd have used heavier gauge wire for a 6 volter than whoever wired this up, although so far nothing's melted. The coming winter will tell me more. Probably at the side of the road when it's wet and dark . . .  Groily
Bill

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Re: Idler gear, dynamo drive etc
« Reply #3 on: 14.10. 2007 15:14 »
Hi, I too have been using JG 12volt conversion on my A10, for well over 18years no trouble have a halogen bulb fitted brilliant lights  .Still have the old chain drive though will get round to replacing it with a belt conversion just to get rid of chain noise & tight spots in chain adjustment, Also be aware that certain pattern idler bushes have a oil scroll all way thru bush & if fitted to inner timing cover can fill dynamo chain comparment with oil even with cork seal fitted,I had this problem after recent build of a new motor, I did notice the difference between the new bush & old genuine part before I fitted them ,But thought cork seal would stop any oil into dynamo drive, Test  drive on the new engine produced an oil leak after 6mls. Oil dripped from dyno housing, I knew right away what problem was & replaced inner case  with a genuine bush ,problem cured...As for wiring I always use trailer wire to make up harnesses, Go for the heavier guage stuff ..You get seven different coloured wires just strip outer casing cut to length & buy heat shrink  to cover new harness. Dave.....

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Re: Idler gear, dynamo drive etc
« Reply #4 on: 14.10. 2007 17:59 »
Very reassuring Gf Dave! We have the same experience. When it comes to wire, I just use black, decent gauge, and get on with it. There aren't many wires on these thing anyway and it hardly takes a mo to sort out what goes where. As long as the joins are OK, soldered where appropriate, and the primary bits, FADE as it were, are done right, and the system is fused, I've never had much trouble. Yeah, you have to think about the internal wiring of the dynamo with some of the 12 volt solid state boxes (well documented), but I'm almost minded to say I don't understand the whole Prince of Darkness thing - I've had more electrical trouble with old cars than old bikes over 35 years. Thank Someone for magnetos; every time I see someone change from mag to whatever expensive alternative (except with V twins for which mags are sub-optimal unless they're 180 degree Vs) I titter quietly with face averted, and hope they've got a plan to get home of nights. Groily
Bill