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Hi Folks,
What would be causing oil to be leaking out from the crankcase breather plug on my 906? I have replaced the plug with a new one and the hose and clamps as well, but it still leaks.
It seems to get worse when I have a cylinder drop out, which is happening very frequently now, but I'm worried that compression is getting through the rings into the crankcase - can anyone help?

Ian

Better, that You check compressing pressures and also that flow passing piston rings..... I dont know english word, but in Finland that is "ohivirtaus mittaus" :laugh:

Finnpaso wrote:I dont know english word, but in Finland that is "ohivirtaus mittaus" :laugh:

Hey Antti,
we could have some little problem with the Finn language :rant: :laugh: :rant: :laugh: ....
Ciao

Ian,

If the crankcase is getting pressurised then you may have broken piston rings. This happened to me many years ago with a bevel drive (OK I know the lubrication systems are very different and have completely different pressures) but the concept is the same. If the crankcase is getting pressurised (hence the consistent oil leak) it must come from somewhere above the piston. So, rings could be broken, hole in piston, all good stuff like that.
When the rings were broken on my old bevel (front cylinder), there was no noticeable performance difference, but the crankcase breather was very active and would spread oil over the rear of the bike.
Also had a little Honda once that had a hole in the piston, the crankcase breather pipe would flap around like a flag in a strong wind, due to the high pressure.

Fraser.

Thanks Fraser, that seems to be it. I'll run some compression tests.....more money.........what a joy these 906's are!

Ian