SOHC.co.uk Forums > CB350/400

Oil leak from head.

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Bradders:
Morning all. I have had an oil leak on my 400/4 for some time which I’ve been trying to ignore but seems to be getting slowly worse. It seems to be coming from the head gasket area, more from the front and blowing backwards whilst riding. Interestingly all the gaskets were changed in September 2019 ( David Silvers kit ) by my old school mechanic, so am quite surprised they have gone already.
Is there anything I can do to fix this or is it head off and renew the gasket? I’m not sure my limited mechanic skills are up to that.

McCabe-Thiele (Ted):
When they banned Asbestos the thickness of the head gasket changed, they did not however change the sizes of the seal rings that don't compress enough.

Bradders:
Thanks Ted. Does that mean if they were replaced it could well still be a problem?

McCabe-Thiele (Ted):
I believe some members have fitted bigger seaks, that might lead to oil starvation to the camshaft so it's a trade off from what I've learnt. A new seal ring will hold the oil back initially then over time, heat cycles you can have a leak

Nurse Julie will know more as will other members, a lot depends on the head gasket thickness I guess.

flatfour:
I lifted the cylinder head on a 400/4 belonging to a friend a few months ago for this same problem. A genuine gasket was bought from DS, together with the two short rubber tubes that seal the oil galleries on either side of the head. I understand that the 350 & 400/4's use these short rubber tubes instead of "O" rings, although as always, I might be wrong?

It has, incidentally stopped the leak!

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