I was just checking things over ready for the commute to work next week, opening up the air box and pulling out a very cruddy air filter I noticed some oil in the bottom of air box, is this normal ? its clean oil and as there is only one way in to the box it must have been put there by previous owner or mechanic on last service.

Any ideas ? will it hurt to leave it ?

Thanks

Bit of oil in the airbox is quite normal, specially after a good run, any oil vapour in the crankcase as it gets presurised usually vents to the airbox via the crankcase breather pipe, so the oily vapour gets beathed again on induction, bit of enviro freindly etc... lots of oil in the airbox means too much oil in the engine - overfilled at last oil change? - and usually gets deposited in the air box through the crankcase breather pipe...

Clean or replace the air filter, wipe out the airbox with some rag or kitchen role, check the engine oil level... check the air box again in a months time!

Thanks Paul, never had it before with any of my Bikes. Checked oil level and it was on max so the overfill theory would fit.

My CCM R30, Suzuki 650 engine, puts oil in to the airbox when filled anything over halfway, specially as it gets quite a spirited ride
Think its more a 'singles' thing as there is no where else for any crankcase pressure to go, no other rising piston...