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[Wheaters]

The amount of pressure your bike seems to be suffering from can surely only come from piston ring blow-by or by a failed head gasket. Is it possible that a compression ring got damaged/broken when the engine was being re-assembled?

[Andy C]

Stinkwheel / Wheaters: Thanks for your input, you both raise good points. It cannot be the head gasket as I fitted a new composite one which was has bene torqued down correctly, so unlikely it is the cause of the problem. My fear is that it might be the rings, hopefully did not break anything whilst putting it back together. Going to pop the timing chest cover off today to check that the gasket is not impeding the scavenge oilway, aparrently that can cause the symptoms. Either way I will get this sorted. Oil mist aside, it really is running well.

[Bullet Whisperer]

It could well be the composite head gasket, as per my original reply. They are very good for preventing oil leaks, but not very strong when faced with compression and I have seen several which have failed in the manner I have already described, one on a bog standard 350 with only 1800 miles on it from new. Nothing will be visible from outside. Don't rule it out!

[Andy C]

Bullet Whisperer - dont get me wrong, I hold your advice in very high regard, just trying to rule out everything else before pulling the head, and if I do I will also fit a new set of rings while I am in there!! Are you saying in your experirnce that I would be better off with a copper head gasket? Also another update, I pulled the timing cover off this morning and found that one of the oil galleries was partially obscured - probably something like 40% by the gasket which I have now trimmed. I gather that this can stop the return pump scavenging properly which can result in too much oil in the crankcase. As I say, just trying to rule out all possibilities. Watch this space.

[Andy C]

Yet another update. After this mornings work to remove the piece of gasket that was partially obscuring one of the scavenge pump oil gallery in the timing case I took the bike for a run this afternoon. Not counting my chickens but no signs of any oil around the breather or anywhere else and I did give it a fair bit of stick during the run. Noticed that the mixture is still on the weak side to I'll go into the carb tomorrow and richen it up a bit, then Ill give a bit more excercise tomorrow. Hoping I have fixed the problem - only time will tell. Another update tomorrow........

[Andy C]

Hopefully a final update on this. Took the bike for a decent thrash this morning. No signs of any oil from the breather or anywhere else. Hopefully job done.