Cylider head gasket blow out-BSA engine

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Layzee Fox
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Cylider head gasket blow out-BSA engine

I have just purchase a Ransomes Fourteen Mk 1 Mower as a non runner. It is fitted with an BSA engine.

I can't find much up with it except every time it fires up within a few seconds the head gasket blows, there is a smell a bit like rubber from the exhaust.

Can anyone tell me what the likely cause is?

wristpin
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Probably old and tired and

Probably old and tired and someone hoping to get away with reusing an old gasket or even a home made one. New gasket, reface the head on a surface plate, plus correctly torqued head screws, should sort it. 

Before you ask, best place for a new gasket is probably Meetens.

Layzee Fox
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Thanks Wristpin, think one of

Thanks Wristpin, think one of the bolts has lost its thread and it is at this point the blow out occurs. Might try to use oversize bolt after rethreading.

wristpin
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Unless the stripped hole has

Unless the stripped hole has been really mauled about , I would use a standard thread insert ( from memory 1/4 UNC - check) rather than go oversize. The drill and tap in the kit are sized to take an insert that will accept the standard sized head screw. That way you keep everything standard and don’t have to enlarge the hole in the head and new gasket. 

Layzee Fox
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Looks like someone else bored

Looks like someone else bored it out before.

Layzee Fox
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Hi Wristpin, Have found a

Hi Wristpin, Have found a slightly longer bolt which should secure more firmly and have a Gasket.

Faces of both cylinder and head look reasonably flat after cleaning up and checking.

Would you recommend that the Gasket be just fitted dry or should I use something like Instant Gasket, red Hermatite or blue Hylomar to both surfaces in case there is any gaps?

wristpin
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If it’s new and of the

If it’s new and of the correct material, fit it dry.

As a general rule of thumb the engaged thread length should be at least one and a half times the screw diameter, preferably twice to be safe.

Layzee Fox
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Thanks Wristpin

Thanks Wristpin