Oil in the combustion chamber

Information relating to the Matchless G9 or AJS Model 20 500cc twin
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Carson
Posts: 31
Joined: Tue Sep 08, 2015 10:04 pm
Location: British Columbia Canada

Oil in the combustion chamber

Post by Carson »

Pulled off the incorrect 4 bolt rocker cover heads to install the correct reconditioned two bolt cover heads on my 1954 Model 20. What do I find but quite a pool of oil sitting on top of the pistons. Before dismantling the engine I did a compression test and both cylinders showed 125 PSI, so I think that is pretty good?
What I did notice was that the heads I took off did not have any oil restriction plugs in the holes that go up to the rockers, whereas the new heads have restricting plugs in both holes.
Is it possible that so much oil was going up to the rockers that it somehow gets into the combustion chamber?
What other factors could account for so much oil in the combustion chambers? No wonder my plugs kept fowling up black.

Carson
Carson
Posts: 31
Joined: Tue Sep 08, 2015 10:04 pm
Location: British Columbia Canada

Re: Oil in the combustion chamber

Post by Carson »

Memo to myself,
Dummy read the previous post before asking a very similar question.
Will definitely try some of the stuff that Craig was told about but would also be interested to know if Craig did find the exact problem?

Also, these pistons are made oval, does anyone know (mine are in the barrel so hard to measure) how many thou out of round they are when new?

Carson
craigcc
Posts: 21
Joined: Wed Oct 03, 2012 10:15 am
Location: CORNWALL UK

Re: Oil in the combustion chamber

Post by craigcc »

I never did find the problem and have started a new thread on the subject - I really need a solution.
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