Motorcycle Repair: Oil in air filter housing, honda shadow ace, combustion gasses

Question
Hi Mark:

I own a 2001 Honda Shadow ace.I went to change the air filter and I noticed oil in the housing.What might be causing this problem?

Thanks

Andrew
andrew197526@yahoo.com

Answer
Hi Andrew,

The cause is  combustion gasses "blow-by" the piston rings and pressurize the crankcase which causes oil to flow to the airbox via crankcase breather vent tube. Fix & prevention: Overfilling engine oil is a common reason this happens. Maintain proper oil level.

Respectfully,
Mark Shively