Hello,
Hoping that maybe someones got a answer for me:
My air filter box gets filled with the engine oil through the Crank case ventilation and then after a small ride the bike gets lots of oil in the carbs causing my spark plugs to get fucked and then it doesnt run properly.

When i get new plugs and clean the air filter box the bike runs like it should until it gets filled again.

-No there is not to much oil in the engine
-Just got my carbs back from cleaning
-Valves are just adjusted.

Can it be piston rings? Is there more than one crank case ventilation ?

could be a couple of things causing oil to blow back through, usually because of a blocked/kinked hose leading to the crankcase pressurising an forcing oil up into the airbox. check all pipes/breathers/vents/etc.

can also be caused by the piston rings not sealing the combustion chamber properly and passing the pressure into the crankcase. to check for this you need to perform a compression test on the cylinders - then again with oil dripped into the bores to seal the rings. quite a lengthy job so best checking breathers 1st.

can't think of anything else that would cause your prob. hope you solve it!!

sorry, forgot to mention that the 2nd compression test with the oil is to establish weather the pressure increases once the oil sealing the bores is added, therefore indicating worn piston rings