Primary Chain

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GuyH
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Primary Chain

Post by GuyH »

My OG 250 parts book says the primary chain should be 1/2 x 0.305 which I believe equates to a 428 chain. However, when I went to fit a 428 chain to the chainwheel it began to pick up after a few links and was slightly riding up the sprocket teeth when just over half way round. on the front sprocket it seems to fit well. Is a 428 chain correct or should I be looking for something else?

Any advice gratefully appreciated.

By the way, if anyone has a petrol tank, oil tank or chaincases for a 1939/40 OG250 I'll be happy to hear from you....
1939 600 OHV 4F, 1956 MKII Square Four, a Healey, 1939 OH 250, 1939 OG 250 plus a couple of OG250 projects, 1920 Ariel V twin project and a variety of lesser makes
JohnnyBeckett
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Re: Primary Chain

Post by JohnnyBeckett »

hi have you got the old primary chain and does that fit OK, then i think you may have the wrong pitch chain :?:
Simon.Gardiner
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Re: Primary Chain

Post by Simon.Gardiner »

Guy
As far as I'm aware 1/2X.305 is as per this link (check the comprehensive set of dimensions on the 'Technical' tab)
https://simplybearings.co.uk/shop/p2003 ... _info.html

Looks pretty similar to what '428' chain is dimensionally - so have you got a duff sprocket?

SG
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'55 Huntmaster, '56 VH, ' 51 VH, '62 Arrow, '80 R100RT, '00 Sprint ST (now with a new Arrow project, and just now those 4-stroke Ariel parts can't even make one running bike...)
nevhunter
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Re: Primary Chain

Post by nevhunter »

Is it binding on the side links or the rollers? There's different diameters for US and IMP chain. Nev
GuyH
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Re: Primary Chain

Post by GuyH »

Thanks all, I'll check the chainwheel again but unfortunately the bike came in boxes of bits and no primary chain. Having had another look at it, it seems to be binding on the rollers and riding up the teeth as if the rollers are a tad too large diameter.
1939 600 OHV 4F, 1956 MKII Square Four, a Healey, 1939 OH 250, 1939 OG 250 plus a couple of OG250 projects, 1920 Ariel V twin project and a variety of lesser makes
nevhunter
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Re: Primary Chain

Post by nevhunter »

It's the roller diameter that varies. Stick to a good motorcycle chain not industrial ones. Don't use split rollers either. They end up in the bottom of the chaincase. Nev
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