Sprocket advice

Information relating to the Matchless G5 or AJS Model 8 350cc Lightweight
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Rupert123
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Sprocket advice

Post by Rupert123 »

Hi,
After a long lay off after having some problems i have returned to my 350 lightweight basket case ,the chain and both sprockets are worn out . On this forum a while back it was recommended to change to a 21 tooth gearbox sprocket the current sprocket is 18 teeth the rear is 55 teeth i also heard the club might have some cheap rear sprockets that need a little bit of fettling.
So a while back i ordered a 21 tooth gear box sprocket a 55 tooth rear sprocket that needs the holes adjusting and a new chain,they promptly arrived
As usual . My fault i never checked what i received till yesterday i found i was sent a 20 tooth front and a 56 tooth rear,having never rode a lightweight is this combination going to make that much difference .

Kind regards,
Martin.
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Rob Harknett
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Re: Sprocket advice

Post by Rob Harknett »

Why not accept what the manufactures recommend ? Are you intending to use the bike for some use it was not designed for ? What would be the difference between 21 - 55 and 20 - 56 ?
What ever non standard sprockets you fit, you will also need a chain length to suit. Otherwise chain tension adjustment's may not be possibly.
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Duncan
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Re: Sprocket advice

Post by Duncan »

Hi Martin, if you calculate the standard ratios (engine, clutch, gearbox, rear wheel - Top gear in the gearbox is 1:1 ratio) you should be able to determine what the difference will be.
Rupert123
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Location: BEDFORSHIRE UK

Re: Sprocket advice

Post by Rupert123 »

Hi Duncan,
Will give it a try.

Regards,
Martin.
Groily
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Re: Sprocket advice

Post by Groily »

Just to say though, irrespective of what's under the primary chaincase, if you went from 18/55 to the originally-proposed 21/55 you'd be going up a heck of a lot - about 16%. If the primary sprocket and clutch drum are standard, I'd guess that might be a bit much on hills, or into head winds, for a motor of modest power? Or are they so desperately under-geared that there's not a problem?
If you went to 20/56 you're talking about roughly 9% up, nett, which might be better.
But, without checking all 4 elements you aren't going to know the reality compared to 'book', as Duncan points out.
Many bikes will easily handle a 5-6% increase in the overall ratio, typically via an extra tooth on the gearbox sprocket, but discretion may have to temper optimism if trying to go too far 'up' in search of comfortable cruising - I know it has with me sometimes!
60 mph in top gear at tickover rpm only works with a hurricane of a tail wind, on the flat or downhill!
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ajscomboman
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Re: Sprocket advice

Post by ajscomboman »

The standard gearing is really really low on the 350, I went to a 19 and I reckon it's pull 20 on the gearbox and 55 rear quite happily. 20/56 it'll also do very well.
Groily
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Re: Sprocket advice

Post by Groily »

ajscomboman wrote: Sat Aug 21, 2021 6:53 pm The standard gearing is really really low on the 350, I went to a 19 and I reckon it's pull 20 on the gearbox and 55 rear quite happily. 20/56 it'll also do very well.
And if that's with a man who fills his shirt (like me) on it, they must be (really under-geared that is.) :D
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