1959 31 primary drive leak

Information relating to the Matchless G12 or AJS Model 31 650cc twin
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Joined: Wed Nov 13, 2019 8:56 pm
Location: West Midlands UK

1959 31 primary drive leak

Postby BrumLoz » Tue Feb 11, 2020 7:46 pm

I need some help again please, not having much luck stopping my primary cover from leaking on my 1959 model 31. I have stripped out the primary cover checking the crank and gear box sealing method. So I see there is a sliding plate with a steel ring around the out put shaft, not to sure how effective this is ?. On the crank there is a collar with a machined spiral presumably to flow the oil back to the crankcase or the primary drive case. So my questions are From the photos

Does my gear box seal plate look correct?

Which direction does the spiral face on the crank collar?

Any help apricated
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Posts: 400
Joined: Tue Oct 24, 2017 11:05 am
Location: DEVON UK

Re: 1959 31 primary drive leak

Postby MalcW » Wed Feb 12, 2020 9:32 am

Have you identified where it is leaking from? One thing that springs to mind is how much oil is in there to start with? There should only be enough to just touch the bottom of the chain on the lower run. Everything else is lubricated by the oil splash. Overfill it and the oil will find a way out.


Posts: 302
Joined: Tue May 27, 2003 12:00 am

Re: 1959 31 primary drive leak

Postby bitza » Wed Feb 12, 2020 4:40 pm

I would also check there are no raised edges around the screw holes caused by over tightening the cover screws, alloy cases are prone to this, if you remove the gasket you can feel the raised lip, if there are, a fine file or a drill bit larger dia than the hole twisted by hand should do the trick.

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