Oil in intake

My crf 250 is running very poor.All valve clearance checked out good.The intake system between the carb and air filter is soaked with oil. Compression seams to be low. HELP!

sure u didnt over oil the airfilter? do a leak down test..

my guess would be that the piston/rings are worn out and you are getting a lot of blow by. The blow by then fills up the drain tube and goes into the intake.

Check and see if your tranny side is low on oil. If it is, the counter balance seal is leaking and the oil is going to the engine side. After awhile the motor side will be over filled and blow oil out the vent hose. Where does the vent hose route too? The air boot! Now you have a pool of oil in the air box and poor performance from the oil being sucked in to the intake charge.

it normally is the right crank seal that is blown if the oil is transferring. But it can also be the balancer shaft seal.

We always replace both, but on my personal bike I had the counter balance seal and not the crank seal. So I just replaced the counter and it solved the problem.


Make sure you "apendix tube" is not simply full and in need of being drained. If it's full there will be no place for the oil residue to "fall out" to, as the blow by goes to your air cleaner.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now