Club Copper Head Gasket Thickness - Thinner Than Advertised

Information relating to the Matchless G12 or AJS Model 31 650cc twin
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Club Copper Head Gasket Thickness - Thinner Than Advertised

Postby CAB » Tue Sep 19, 2017 9:50 pm

Hello

I've just stripped my 1961 CSR to cure some oil leaks. I originally thought that the leaks were coming from between the crank case halves but it looks like the composite head gasket failed. I don't know if this was due to the previous owner not torquing the heads down before I owned it but the copper fire ring was egg shaped between the inside studs and the fibre part had split between the push rod and oil feed holes.

I decided to replace the composite head gaskets with solid copper. Originally I was going to get a set from AMC Classic Spares with Viton O'rings but they are out of stock so I ordered some (1.5 mm thick without O'rings) from the club instead. I checked the stack up of the barrel spigot (3.37 & 3.12 mm high on the sleeved barrels that are on the bike and 2.74 & 2.61 mm on an old spare set) and the depth of the recess in the heads (2.33 & 2.32 mm on the heads on the bike and 2.30 & 2.35 and 2.36 & 2.37 on two sets of spare heads). I also checked the 1.5 mm thick gaskets rather than just fit them and these are only 0.88 mm thick.... If I had fitted these as is, the gaskets wouldn't have been clamped when the head was torqued down.

Have I just been supplied with an alternative thickness of gasket by accident or is this as they come? I can only see 1.5mm thick copper gaskets advertised on the website. I have contacted the club spares scheme via email but haven't had a reply yet.

Thanks

CAB

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Re: Club Copper Head Gasket Thickness - Thinner Than Adverti

Postby g5wqian » Wed Sep 20, 2017 6:52 am

The copper gaskets I told the club spares about 2 years ago that they were wrong thickness .
I used some in my model 30 and no good due to spigot interfering with head recess.
I have since put a pair of club composite head gaskets on and no problem with tem.
All I can say is if you want higher compression use the copper gaskets and skim the barrel spigot down , otherwise forget those particular copper gaskets and find some genuinely 1.5mm thick types.
The composite types are 1.7mm thick , and my engine doesn't suffer pinking much if at all now .

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Re: Club Copper Head Gasket Thickness - Thinner Than Adverti

Postby g5wqian » Wed Sep 20, 2017 7:01 am

Forgot to say be careful if effectively lowering head that valves don't hit pistons

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Re: Club Copper Head Gasket Thickness - Thinner Than Adverti

Postby 1608 » Wed Sep 20, 2017 12:32 pm

I've used composite gaskets for some time and never had a problem, head must be re-torqued though as you know. It is necessary to enlarge the push rod hole in the gasket otherwise the gasket canl chafe the alloy push rods. I tried solid copper with the 'O' rings but they just leaked oil.

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