Motorcycle Repair: oil leaks from the air cleaner at higher speeds., check oil level, crankcase oil

Question
I have a 1988 Honda Shadow vt600c. It was dropped in October of 2004. Now, when it reaches speeds of 60 mph or higher, oil begins to spray out of the bottom of the air filter housing. I thought of changing the piston rings, but if the problem can be fixed another way that would be wonderful.
Please help me.
Thanks,
 Don Way

Answer
Hi Don,

Piston rings are not the cause. Exhaust gasses that blow-by piston rings cause the crankcase. Blow-by is a normal event in all piston engines, even new engines.

If in doubt about the condition of the engine, check cylinder compression to learn the sealing properties of the combustion chambers. Follow with a leak-down if compression readings are not within service limits.

When oil is over filled, this pressure can send oil vapor and oil to the airbox via crankcase vent tube.

This also occurs when fuel left in the carburetors varnishes, causing fuel to over fill flaot bowls and leak into crankcase.

Oil will flow to the airbox when the MC is layed over, too. Normal crankcase venting will blow oil from the airbox drain, especially when the airbox and drain have excessive amounts of oil build-up.

Check the airbox for the pressence of oil/fuel sediment. Drain and clean the airbox accordingly. This is part of routine maintenance. Clean or replace the air filter as necessary.

Check oil level on level ground with the MC positioned upright. Adjust oil level accordingly.

Respectfully,
Mark Shively