1963 G80CS O-rings at barrel base

Information relating to the Matchless G85 500cc Heavyweight, AJS 7R, Matchless G45 and Matchless G50
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Location: BUCKS UK

1963 G80CS O-rings at barrel base

Postby jack clegg » Fri Aug 31, 2018 12:36 pm

Dear Folks,

Has anyone else found problems with the two thick O-rings which fit in the lower pushrod recesses in the cylinder barrel? The ones I just removed had been cut on both ID & OD by the edges of the recesses in the barrel. When I reassembled with new ones, the barrel did not appear to seat fully home at the base. I could get a 3 thou gauge in the gap (at 40 foot pounds). Also the pushrod clearance had increased. I lifted the barrel again & found the new ones deformed at their circumference. I ended up slicing away the outer circumference of the O-rings & refitting, but am not really happy with this solution. When I first got the bike I found these O-rings were missing. I'm wondering if these O/S O-rings were the reason why.
I have not yet had the opportunity of consulting with Steve at AMCCS, maybe Monday if he don't see this post. I cannot believe they are the correct size for the application. You should see the mess these old O-rings are in.

Regards Jack
John Marshall

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