hi steve,

i still have the same problem, oil through breather in airbox after piston job. not as excessive as before but still.

only thing i can think of is worn out valveguides and valves. that is the only area where exhaustgas can enter the cranckcase through the cilinderhead.

overhaul the head is expensive: just new valves and -guides is 250. get more expensive if valveseats need replacement.

am flat broke and still unemployed at the moment so i try to find a used cilinderhead. got a guy who has one and have another offer for a complete engine with 12kkm on it. might do that. my engine is over 85000kms so....

..2bcontinued...

cheers,
sanderd

woe woe woe
 

hi sorry to hear not fixed yet my bike has (has had a few owners before me so who knows?)about 26.000 kms now had about 12.000 kms when i got her mid 2008 also just put a new genuine air filter (ive got a yamaha sr500 as well in bits )as i had this problem once on the sr500 the air filter was clogged and the path of least resistance was the carbs were drawing air from the crankcase rather than thought the clogged filter fixed when i put a new filter on the sr500 see if you can get a mechanic to do a leak down test for you thanks for your reply ill let you know if i strike lucky and find a cure steve

hi again could it just be the valve stem oil seals are not sealing? through wear or damage? would this allow compression pressure to seep pass and pressurise the crankcase? this would not show up on a leak down test as it is done at tdc when the valves are sealing against the valve seats did you not check/change the valve stem oil seals when you rebuilt the engine i wonder if this is my problem? thanks steve