Chain case - 1954 G80s

Information relating to the Matchless G80 or AJS Model 18 500cc Heavyweight.
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StephenG80
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Chain case - 1954 G80s

Post by StephenG80 »

Hi - I have a bit of bitza G80s 1954

Q1: just wondering if it is straight swap re replacing the tin chain case with an aluminum one (which presume do not leak?) or did those only come in with the later gene G3 and G80s in which case they won't work/fit on the earlier models?

Q2: I was reading somewhere about replacement rubber seals for the tin primary with a lip that goes between the faces - do these solve the problem re leaks and are they available via the spares scheme?

Look forward to any advice.

Stephen
bob
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Re: Chain case - 1954 G80s

Post by bob »

I cannot help on Q1
But Q2
Yes the improved seal from The spares scheme does indeed seal . Ive got one on my 53 M16
The screw for the band connector will need replacing with a longer one tho as the seal is thicker .
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Pharisee
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Re: Chain case - 1954 G80s

Post by Pharisee »

Stephen G80 wrote:Hi - I have a bit of bitza G80s 1954

Q1: just wondering if it is straight swap re replacing the tin chain case with an aluminum one (which presume do not leak?) or did those only come in with the later gene G3 and G80s in which case they won't work/fit on the earlier models?

Q2: I was reading somewhere about replacement rubber seals for the tin primary with a lip that goes between the faces - do these solve the problem re leaks and are they available via the spares scheme?

Look forward to any advice.

Stephen
Assuming your G80S had a dynamo mounted behind the cylinder, the aluminium chain case won't be any good to you as they are for alternator models and there's no provision for the dynamo drive chain.
Also, the drive side crankcase half has an extra 'boss' on it for the chain case mounting stud.
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StephenG80
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Re: Chain case - 1954 G80s

Post by StephenG80 »

Thank you Bob and Pharisee for the insight - I'll definitely go for the new seal then

Another question - should there be a fibre washer between the internal spacer stud in the chain case and the inner side of the chain case? Mine has one fitted and as it has compressed, it has allowed the slack to enter and all the bolts have slackened off. When I re-assemble it all I am intending to not replace it. I can find any listing for such a washer in the spares listing. Any ideas?
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Pharisee
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Re: Chain case - 1954 G80s

Post by Pharisee »

When I put my 55 M18S back together with the new, revised seal, I had to add an extra washer or two (metal, not fibre) under the long nut between the the two chain case halves to allow for the thickness of the seal. That way the case wasn't distorted when the outside nut was tightened. The tubular spacer should go behind the chain case, between the engine plate and the inside chain case half.
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thornebt
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Re: Chain case - 1954 G80s

Post by thornebt »

It also looks better if you replace the central nut on the outside of the chaincase with a half nut - as the stud won't be long enough for a full nut. Cheers. Bruce.
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Harry44
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Re: Chain case - 1954 G80s

Post by Harry44 »

thornebt wrote:It also looks better if you replace the central nut on the outside of the chaincase with a half nut - as the stud won't be long enough for a full nut. Cheers. Bruce.

Is that CEI thread ? I was thinking a dome nut would look pretty on mine.
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spookefoote1956
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Re: Chain case - 1954 G80s

Post by spookefoote1956 »

Hello again. What is the thread for the stud and where can I get a half nut?

Cheers, Chris
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