Timing chain adjustment

Sakura

Well Known and Active Forum User
Non-VOC Member
Bill,



Reason is, folklore has it that the chain is 1/2 x 5/32". But I am not even sure that size ever existed; it's certainly not been available for decades.

Peter B
1/2 X 5/32" certainly is a size but quite probably doesn't exist new any more. I recently fitted a used length on the primary chain of a 1922 2 stroke Levis.
 

A_HRD

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VOC Member
Thanks for that Sakura. Interestingly, I am advised that Maughan's made a batch of A Twin mag-drive sprockets not so long ago. They are 1/8" thick.

Peter B
 

Sakura

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Non-VOC Member
Obviously 5/32" is 1/32" wider than 1/8". I wonder if the 5/32" chain is meant to run on 1/8" sprockets to allow for slight misalignment on short run timing chains?
 

Dinny

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VOC Member
I was just looking though some old MPH articles (217) by Bob Stafford as I’m assembling my A Comet and found the below which maybe of use. Note the last paragraph.
 

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A_HRD

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VOC Member
Thanks Dinny,

What you refer to is part of the folklore to which I refer above. Richardson says much the same.
Bob also says in MPH 630 :- 3/16" x 1/2"!!

I too have considered Sakura's point while researching this issue for The Book.

Either way, given that 5/32" seems to have been unavailable for decades - and I have yet to find anyone with an A Twin sprocket greater than 1/8" - it is safe to say that there is little alternative now but to use 1/8" - regardless of what the original was.... (and check alignment carefully!).

Thinks I'll go for a belt conversion!

Peter B
 

Marcus Bowden

VOC Hon. Overseas Representative
VOC Member
Just goes to show how a couple of days away in Paris with the kids things certainly get a head of me.
Bill make sure you fit a spring/lipped Gaco seal into the inner chain case as I used nearly a gallon going to sea Proff Higgins in Sweden and then he gave me another gallon to get home with Got the sizes from Bob Stafford as he was always helpful to me also he congratulated me in using the "A" so extensively as he used his traveling back and forth to Germany when in the forces and they cam be got better with today technology . Or there is another mod that Robert Watson passed onto me and that was connecting a drain line to a "T" banjo bolt directly into sump, mine had to be a "T" as there was another from the "COFFIN" oil separator (threw away the coffin lid. ! )
FRONT CAM BEARING INTO CHAIN DRIVE TO MAG/DYNO
IMGA0748.JPG


WRONG PHOTO BUT IT IS ACTUALLY OUT SIDE STENA LINE HOOK OF HOLLAND 18th October 2013 PRIOR TO AGM THEN HAD TO LEAVE EARLY TO CATCH FERRY AT PORTSMOUTH FOR FRANCE.

IMGA0746.JPG


Peter I do like your mag/dyno platform and certainly looks right, may I pass on a little tip that I had done when Colin Jenner did the restoration on Old Harry EAR 2x3=6
Quoting,
Drill 1/8" drain holes from what was the mag base to the side of the mag pick/ups I think they emerge at an angle as Alace Leney who rode HJO 500 to the NZ annual last year found to his frustration water in the mag armature housing, also silicone rubber in the original drain hole. The bikes were parked in the rain for nearly two days while we drank beer and ate.
That goes for you too Bill.
 

billirwinnz

Well Known and Active Forum User
VOC Member
Thanks Marcus

Alice warned me about the hole and I blocked mine but I've since just fitted a new magdyno body and drilled a hole in what will be the underside.

As far as chains go I have been using this handy calculator to check chain loading.

http://www.renoldchainselector.com/ChainSelector I was happy to find a similar result to my own crude calculations. As you can see from the attached result the maximum force (assuming about 200w load) is only about 20lb which is well within the strength of a typical cycle chain.
 

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billirwinnz

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VOC Member
Bill,

Coincidentally, I've been struggling with the Twin mag-mounting for a few weeks now. After looking at endless photos and sketches, rubbings and samples, I made my own. Great, progress at last. NOT. Finally, I came to the only possible conclusion that the 1/2" slot is wrongly positioned on the original brackets. This limits any movement of the mag-mounting, (which needs to be in line with the two sprockets) and actually makes it cant over at an angle. So adjustment is severely limited. (I accept though that it could be an issue with the jigging of my frame at the front!).

Finally, I made a mock-up with the offending slot re-positioned and it works like a dream. So then I bought a piece of 1/4" alloy channel, 4 inches across, and marked it up as per the photo. I've since got it roughed out and hope to have it all fitted-up soon.....

I'd be interested to know if you've got full range of movement (in line with the sprockets) on your original mag-mounting bracket?

Peter B

View attachment 25457
Hi Peter

The 1/2" slot on my mag mount doesn't allow full adjustment either. It's not an original but was perhaps copied from one. I have had to remove 1/16" from the top rh corner in order to get full adjustment. I'm hoping that along with a newer chain will restore correct tension.

Cheers Bill
 

A_HRD

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VOC Member
Bill,
Thanks for that info - exactly as I was experiencing - only more than 1/16".
Peter B
 

Robert Watson

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VOC Member
Mine was a similar experience. I tried to fit the mag mount bracket that came with the bike and thought I must be doing something wrong. I called the previous owner and had a conversation. He told me it didn't have one so he had this one made by a very experienced metal fabricator.

I made a new one that worked properly. I had a very used chain but sprockets that were quite usable, so looked all over for a chain. The local bike shops had nothing but Chinese chains. I found some very nice German chain but really didn't need the 25 meters they wanted to sell me. Explaining my woes to another guy restoring an A twin, he said he had a nice new spare in hand which he would send me. When it arrived it seemed that someone had got a nice new spare, put it on the bike and diligently put the old VERY tired one in the box. Worse than the one I had. In the end I ordered one from Conways........ They assured me it was a quality chain. It duly arrived. Chinese bicycle chain...... I gave up and put it in, which reminds me, I should look at it.

And A-HRD, this was the other thing I was going to talk to you about!
 
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