Oil return bleed valve - Its confusing me !

Information relating to the Matchless G11 or AJS Model 30 600cc twin
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DerekAJS30
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Posts: 37
Joined: Mon Sep 11, 2023 4:07 pm
Location: Devon

Oil return bleed valve - Its confusing me !

Post by DerekAJS30 »

I'm rebuilding my Model 30 enging and have the oil pumps in bits. The aluminium housing that holds them has a small screw at the left end with a spring and ball identified as a return bleed valve. There is a gallery behind the ball valve that only seems to go to a minute hole in the left pump and could possibly go to a second one in the right pump. I've put a very thin screwdriver up the gallery but it only goes to the centre of the aluminium block and not the the right pump.
So i have several questions of you guys "in the know"
1, What on earth does the ball valve do ? - the tiny little holes seem insignificant.
2. Should the gallery go to both pumps ?/ hence mine is blocked half way along.

I'm concerned because this engine has suffered from oil issues in its previous life and i'm trying to address all the possible issues. Frankly I have no idea what this bleed valve is for, or its effect if not operationg correctly.

If i have an issue i guess i can get the gallery unblocked somehow.

All help very welcome.
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Duncan
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Joined: Thu Jul 10, 2003 1:00 am
Location: HAMPSHIRE UK

Re: Oil return bleed valve - Its confusing me !

Post by Duncan »

Its a non return valve, its there to allow the feed side of the pump to prime the scavenge side but prevent reverse flow. With the pump stripped down you should be able to blow air/carb cleaner/WD40/etc through the channel.
DerekAJS30
Member
Posts: 37
Joined: Mon Sep 11, 2023 4:07 pm
Location: Devon

Re: Oil return bleed valve - Its confusing me !

Post by DerekAJS30 »

Thanks Duncan, Thanks for the technical info. It was indeed blocked. It took a special tool made by a local engineer to clean it out. All done now, pump rebuilt with improved tolerances, and will be fitted this weekend.
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