Oil feed to valve rockers on g12

Information relating to the Matchless G12 or AJS Model 31 650cc twin
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Clarkieg12
Posts: 3
Joined: Sun Mar 20, 2022 4:44 pm
Location: Devon

Oil feed to valve rockers on g12

Post by Clarkieg12 »

I’m having a rattling problem which seems to be coming from the cylinder head area.
I have removed the tapet covers and found the area really dry ie very little oil in the area.
I have removed the heads and checked the head gaskets for the small oil hole which is present, however on checking this small oil way in the head there seems to be what look like flow restrictors inserted.
I have tried inserting a thin wire in these to see if there is a hole but there is not one. These inserts are green in colour.
My question is are there supposed to be inserts in this oil way as it looks like they are completely blocking the oil flow to the tappers and would explain why I am getting this top end rattle due to lack of lubrication.
The engine had an extensive rebuild (before I aquired it) and from what I can see is in very good condition.
My thought is that these plugs in the oil way were installed when the head was cleaned and should have been removed before fitting.
Any help or advice would be greatly appreciated.
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Duncan
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Joined: Thu Jul 10, 2003 1:00 am
Location: HAMPSHIRE UK

Re: Oil feed to valve rockers on g12

Post by Duncan »

There were various changes to the metering plugs in the cylinder head over the years, for one year only three were used but generically speaking there should be one in each oil way, they are brass, early ones had a flat on one side and current ones have a small pilot hole. The green item sounds like blasting plugs or corrosion.

This picture should help you visualise the plugs: https://www.amoc-parts.com//store/comer ... duct=21349

Can you test to see if they are letting any oil/carb spray/WD40/etc past, generally twins have a well oiled top end.
Clarkieg12
Posts: 3
Joined: Sun Mar 20, 2022 4:44 pm
Location: Devon

Re: Oil feed to valve rockers on g12

Post by Clarkieg12 »

Duncan, thanks for the information. Will have a look in the morning and report back.
Maybe I need a thinner probe, like a needle to test this.
I have to say the wire I used was very thin but maybe not thin enough!
Thanks for your help and the swift reply.
Jon
Clarkieg12
Posts: 3
Joined: Sun Mar 20, 2022 4:44 pm
Location: Devon

Re: Oil feed to valve rockers on g12

Post by Clarkieg12 »

Duncan, I’ve checked these inserts and they are metering plugs.
I’ve now managed to get a needle to go through the metering holes.
It looks like these holes were partially if not fully blocked by what I do not know.
I can now get the needle fully in without difficulty.
Will get the top end reassembled and hopefully my problem will go away and I can get out on the bike this summer!
Thanks again Duncan, your help has been invaluable.
Jon
Last edited by Clarkieg12 on Mon Mar 21, 2022 10:22 am, edited 1 time in total.
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