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Engine sprocket & shock absorber
#771744 04/22/19 3:56 am
Joined: Aug 2016
Posts: 73
BevanC Offline OP
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Hi folks,
I posted this query on the AOMCC forum but am a bit uneasy with the reply, so would appreciate another opinion:

I bought a 23 tooth sprocket to replace the 19 tooth one on my 1950 VB; but having dissembled the primary side, I find that the lobe profile is not the same, so it doesn't match up with the shock absorber/sliding member. The lobes are different widths and have a different curvature - the load bearing surface would be much less. I gather the 23 tooth sprocket is probably for an earlier (pre 1945 Ariel).

This video shows the issue:

https://youtu.be/LC15GBjO9u4

My question is: am I safe to fit this on or not ? I've been told - yes, people have done this, but I'm concerned. There is very little contact surface so it will wear rapidly - but is it likely to be able to perform correctly and transmit the engine power safely ?

Or should I admit I stuffed up and get a suitable sprocket made ?

Cheers, Bevan

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Re: Engine sprocket & shock absorber
BevanC #771745 04/22/19 4:55 am
Joined: Nov 2011
Posts: 5,997
Likes: 31
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Originally Posted by BevanC
I find that the lobe profile is not the same,
I hadn't seen your AOMCC post until just now but you'd be well advised to ignore what you read there. The attached photograph is of the two pieces of a 19T sprocket I bought for my 1928 Ariel, which looks very much like one of yours. The problem was just the sprocket itself originally came and it doesn't match the cam I already have with the 23T on my bike, which looks like the other one of yours. Once I discovered the problem I was able to buy the mating cam as well as the spring, which also is different. .

Anyway, there seem to be early (as in pre-'29) and late (as in '29 through at least the time of yours) sprocket assemblies. Mis-mating sprockets and cams is the wrong thing to do.

Attached Files Sprocket.jpg
Re: Engine sprocket & shock absorber
BevanC #771747 04/22/19 6:10 am
Joined: Aug 2016
Posts: 73
BevanC Offline OP
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Hi MM,
Thanks very much for confirming my gut feel that fitting this up is the wrong thing to do. They must have been designed to have mating surfaces, anything else is just not sensible.

While I lack British motorcycle experience, the Physics teacher in me was screaming that this was not o.k. !

I'll go with my initial plan and get a correct sprocket made locally

Cheers,
Bevan

Last edited by BevanC; 04/22/19 6:10 am.

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