leak from cyl. head joint

Information relating to the Matchless G3 or AJS Model 16 350cc Heavyweight
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jimh
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Location: Merseyside UK

leak from cyl. head joint

Post by jimh »

I decided to sort out a slight cyl. head joint oil leak on my 1955 G3LCS, unfortunately things haven't gone to plan and I wonder if any other members have had the same problem and would appreciate any suggestions.

The CS models don't have a head gasket and need to have a good joint between cyl. head and cyl. barrel, whilst trying to 'lap' the joint I noticed the top fin of the barrel and underside of the cyl. head were rubbing together so I measured the raised shoulder on the barrel and it's corresponding recess in the cyl. head and both came out at 2.3 mm, so it seems when tightening the head down the top of the barrel and cyl. head are stopping the joint sealing properly.

The barrel fitted is an Alfin stamped AL-FIN AFD 154, would this be a normal part for the CS models?
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dave16mct
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Re: leak from cyl. head joint

Post by dave16mct »

My '57 CS (shortstroke) engine isn't stamped Alfin but I thin my '56 (longstroke) trials was. I use a copper head gasket from AMC classic Spares on mine.
Dave.
jimh
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Re: leak from cyl. head joint

Post by jimh »

Hi Dave

I was looking in the spares section and noticed that the head gasket for the 1939/48 350's (012268) is a plain copper ring, is that the sort of thing you used?

The recess in my bike's cyl. head is 3 1/2" O.D. would anybody know if that gasket would fit on a 1955 cyl. head.

Thanks Jim
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dave16mct
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Re: leak from cyl. head joint

Post by dave16mct »

No, mines a 500 short stroke and uses the gasket for late short stroke road models. I have looked at AMC Classic Spares and they don't list one for your bike. Yours will be similar to the road model but with different stud hole spacing. I'm hoping Rob S. will help with this as he uses copper gaskets on his CS's. You may have to make one using the base gasket as a pattern?
Dave.
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dave16mct
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Re: leak from cyl. head joint

Post by dave16mct »

Thinking about it......I think it's the barrell base studs of the road model which has the different spacing. The head bolts may be the same as the C/CS through studs. I'll check this this later as I have a comp 350 head and barrell.
Dave.
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dave16mct
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Re: leak from cyl. head joint

Post by dave16mct »

OK , I've just checked and the standard G3LS headgasket is too big. The centre is 3 5/8" dia. The spacing is correct but the holes are smaller. My barrell has the same Alfin markings. If it was me I'd make a gasket.
Dave.
jimh
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Location: Merseyside UK

Re: leak from cyl. head joint

Post by jimh »

Thanks for looking Dave.
Jim
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dave16mct
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Re: leak from cyl. head joint

Post by dave16mct »

This is how the master does it! (Millyard)

Dave
jimh
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Re: leak from cyl. head joint

Post by jimh »

Thanks for the pointer to Millyards utube site, very interesting, as you say it looks like I will have to make my own gasket, on checking the cyl. head again it seems it may have been skimmed at some time in the past.
Jim
56G80S
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Re: leak from cyl. head joint

Post by 56G80S »

IKBA, and expect Rob Swift to jump on me from a height, as I haven't had one of these machines but I dreamed that someone had posted years ago, along these lines:

"copper wire as a circle round the spigot on the barrel and then torque it down"?

Had Linda put magic mushrooms in my food?

Johnny B
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