I'm resurrecting this thread as I've just found the cause of my A10 throwing oil out of the crankcase breather in quantities enough to slather all over the back tyre dangerously. Any comments on the likely root cause or on my proposed fix would be welcome.
The engine doesn't smoke especially badly and a borrowed compression tester showed both cylinders the same and OK. I checked the breather top hat/cork and all fine. However when the barrels were taken off, I found I could get a 2 thou feeler gauge into the joint between the two crankcase halves where the breather gallery crosses into the left crankcase-half. The nut in the crankcase mouth was not 100% tight, though not loose by any means. I loosened it off completely and the feeler would go right into the joint. Conclusion - oil is being blown into the joint, thence into the breather gallery and out via chain onto the tyre.
I know I should split the crankcases and do a proper engineering fix with an 'o' ring....however I intend: washing out the joint with thinners, get as much sealant as I can into the joint (using some low viscosity Samsonal sealant), tighten up the crankcase mouth nut very tight (with flat washer and loctite on threads), clean excess sealant off.
Any downsides I've not thought of?