Composite Head Gasket

Information relating to the Matchless G2 or AJS Model 14 250cc Lightweight
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Composite Head Gasket

Postby Martin.S » Thu May 02, 2019 6:34 pm

The composite head gasket that the club offers - is it coated with a lacquer or sealant or is putting something like Wellseal on it recommended?

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Re: Composite Head Gasket

Postby ajscomboman » Thu May 02, 2019 7:57 pm

I just lightly smear them with copperslip.

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Re: Composite Head Gasket

Postby Martin.S » Wed May 08, 2019 2:40 pm

As I only had the one reply (Thank you Rob) I took my head gasket along with me when I went to pick up my head after having had the seats cut and asked the proprietor ( a long time motor mechanic) whether to coat the gasket. He thought that this material used to be called Hallite and when they first used them they too covered then in copper grease and complained to the manufacturer the gaskets weren't lasting very long - It turns out they were meant to be fitted dry.
So you pays your money and takes your choice.

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Re: Composite Head Gasket

Postby raffles » Wed May 08, 2019 6:42 pm

If I remember correctly Hallite was made of a major amount of asbestos.
Like Rob I also coat the modern version but I just use grease AND touch wood
have not had a cylinder head gasket fail. So as you say .You takes your choise
Tony

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Re: Composite Head Gasket

Postby ajscomboman » Wed May 08, 2019 6:51 pm

The only composite head gaskets I've ever had fail is on the 63 CSR which runs 10.25 : 1 other than those I've yet to have a set fail and all have been lightly smeared with copper grease.

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Re: Composite Head Gasket

Postby Martin.S » Wed May 08, 2019 8:54 pm

Ok so I'm just throwing out the question - Why lubricate it?

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Re: Composite Head Gasket

Postby MalcW » Thu May 09, 2019 8:27 am

Martin.S wrote:Ok so I'm just throwing out the question - Why lubricate it?


Someone with a definitive answer will be along soon, but I'm guessing it's to make life easier when you next have to remove the head.

Malc

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Re: Composite Head Gasket

Postby Mick D » Thu May 09, 2019 8:52 am

Hi

I guess it helps it to move slightly as it settles and spreads during torqueing too.

Regards Mick

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Re: Composite Head Gasket

Postby Woodland » Thu May 09, 2019 6:49 pm

I have just replaced mine on a 1961 Matchless G2, left it dry and just torqued it down, seems ok / no leaks etc

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Re: Composite Head Gasket

Postby Ozmadman » Thu May 09, 2019 10:00 pm

Woodland wrote:I have just replaced mine on a 1961 Matchless G2, left it dry and just torqued it down, seems ok / no leaks etc

Will need to torque it down at least one more time after a shortish ride and when it has cooled down to cold (overnight). A real pain I know but if you don't you may see it leaking again, I had to do mine twice!! Slightly slacken off the head bolts first and re-tighten/torque them one at a time diagonally
Paul
1960 Model 8
1974 Yamaha RD250B US Model 6 speed

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