G2CSR cylinder head gasket not fitting

Information relating to the Matchless G2 or AJS Model 14 250cc Lightweight
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G2CSR cylinder head gasket not fitting

Postby WiltshireMike » Tue Dec 22, 2020 3:51 pm

My '66 G2CSR appears to have had a few ££ spent on the engine before I took ownership, with a freshly honed standard bore and what appears to be a new piston. As a result I'm not planning to dis-assemble it beyond a quick look-see and will continue to re-commission rather than rebuild what seems to be a genuine original.

All good you may say, but the new head gasket will *just* not fit over the cylinder barrel spigot and, looking at the somewhat distorted copper sealing ring of the removed gasket it appears that didn't either. The barrel spigot measure up as 3.094" and matches nicely with the cylinder head recess of 3.095" (both +/- a thou) so I'm thinking the culprit may be the head gasket which I bought from the Club Spares scheme.

Has anyone else had a similar problem, or specifically NOT had the problem with a gasket from a different source?
Last edited by WiltshireMike on Tue Dec 22, 2020 5:35 pm, edited 1 time in total.

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Re: G2CSR cylinder head gasket not fitting

Postby ColourNcoat » Wed Dec 23, 2020 5:03 pm

Hi Mike, my gasket was also tight and did distort whilst fitting it.
Regards Roger.
Roger

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Re: G2CSR cylinder head gasket not fitting

Postby spitfire » Wed Dec 23, 2020 7:09 pm

i have had nothing but problems with these composite head gaskets, you are right they dont fit properly. If you distort it while fitting it ,it will not be seated properly and will blow out at some point. I have got through three of these because of this. Steven surbey at amc classics spares sells solid copper head gaskets for the lightweights and they are a perfect fit, they just drop onto the studs. I have never had a problem since.

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Re: G2CSR cylinder head gasket not fitting

Postby ColourNcoat » Thu Dec 24, 2020 12:53 pm

spitfire wrote:i have had nothing but problems with these composite head gaskets, you are right they dont fit properly. If you distort it while fitting it ,it will not be seated properly and will blow out at some point. I have got through three of these because of this. Steven surbey at amc classics spares sells solid copper head gaskets for the lightweights and they are a perfect fit, they just drop onto the studs. I have never had a problem since.



Thanks for the heads up. Shall look into this before I get round to firing it up :beer:
Roger

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Re: G2CSR cylinder head gasket not fitting

Postby WiltshireMike » Thu Dec 24, 2020 2:56 pm

Thanks for the replies, guys. I was reticent about fitting a solid copper gasket mainly on account of spreading the crush load out over a much larger area and risking poor sealing around the oil pressure transfer hole which is very close to the gas seal. IMHO the composite gasket is the correct approach, but just needs to be to the correct internal diameter. Do we know who the manufacturer is?
Mike

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Re: G2CSR cylinder head gasket not fitting

Postby spitfire » Thu Dec 24, 2020 3:18 pm

The original factory fitment was a solid copper gasket, and as i say i have never had a problem with these sealing. I have no idea who makes the composite ones.
I dont think i would go back to using these now, even if they did fit.

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Re: G2CSR cylinder head gasket not fitting

Postby g5 butch » Wed Dec 30, 2020 3:40 am

I have had 2 head gaskets purchased at different orders that wouldn't fit over the spigot of my G5, I'm lucky I had extra gaskets that were correct (keep spares) to finish the assembly of the motor. Other than the fit of the copper seal with the two gaskets have had no problems with the composite gaskets.

Cheers Wayne

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Re: G2CSR cylinder head gasket not fitting

Postby ajscomboman » Wed Dec 30, 2020 9:49 am

If you guys can give us a specific dia measurement of the spigot for both 250's and 350's we'll check stock and then report back to the suppliers if we find the same issue. Rob

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Re: G2CSR cylinder head gasket not fitting

Postby WiltshireMike » Fri Jan 01, 2021 11:56 am

Hi Rob,

Thanks for helping out. My '66 G2 spigot diameter measures 3.091" / 78.51mm

Mike

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Re: G2CSR cylinder head gasket not fitting

Postby clanger9 » Fri Jan 01, 2021 5:54 pm

78.6mm here (250 barrel).
1989 Moto Morini Dart 350
1993 Ducati 750SS

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