Oil leak from crankcase vent

[bo6o]

Hello to all. A few days ago I bought this nice bike - Diversion 600cc, '92. And there are some issues, that need to be fixed.
The previous owner said he made a carburettor sync, but there are still some, I think detonations on idle speed. They were noticed only from the left exhaust, but when I changed the air filter - they started to happen from both. Anyway - the bike is running. Sometimes happens that not all cylinders work. I changed the sparks also - the old ones were black. Sometimes it starts to run smooth and fast only after 3000rpm-before that it's like choking.
And the biggest problem is that oil is leaking from the crankcase vent. The reason that I'm most affraid of is that the engine is overheating. No warning lights are glowing, and there is no temp. meter. Can you advice me what to look for, to fix this issues. From where do I adjust the fuel/air mixture?

[amorti]

Most common reason for that leak would be overfilled oil. Check the level.

[bobh]

Sounds very much as if it's running too rich. Normally you wouldn't have to adjust the mixture - check first of all that the choke is not sticking partly on, possibly due to the slide on the carbs not returning fully.

[bo6o]

OK, thanks. Tomorrow I'll change the oil and fill it to the right level ( I hope this is the reason). As for the choke - I'll check it, but I think if that is the reason, the bike should work in higher rpm? The idle is about 1000rpm. And if it's not - how do I adjust the mixture?

[CD]

Amorti posted some fixes for the 600 crankcase breather system. You need to be 100% sure the big pipe isnt blocked with oily emulsion. His fix was to use a new hose with less tight curves.

Too many short journeys make it worse. Also check the clutch lever seal on the clutch cover is AOK. Leaks there let in water which boils off and adds to the breather pipe emulsion problems. It also messes up the roller bearings in the clutch mechanism.