Just bought an 2009 Kawasaki KLX250SF, checked the air filter and it has pooling of a fuel/oil mixture at the base of the spark screen. Feels like oil and smells like fuel. The condition of the filter at the base has been affected by sitting in this mixture as it's eaten away at the foam. This airbox has hoses from both the pair valve and crankcase breather. Is this a normal condition?

 

It is if the filter is very old. And it looks old, like me🤣

 

If the filter is deteriorating replace it. There usually is a bit of oil at the bottom, because it may drip from the air filter - air filter oil. I don't know that I've ever really seen much oil from the breather and there won't be any oil from the PAIRS because it is drawing air from the air box and there is no fluid between the air box and the reed valve. If the bike runs well there really shouldn't be any fuel pushing back that far.

I'd say replace the filter, do another foam one if you ride in dusty conditions, not a K&N. If you mainly street ride a K&N is fine. Oil the filter and put it in. I doubt there is any issue. I'd say the air filter deterioration is purely from age, not from the oily stuff. Good chance it is a 2009 air filter. Get a new one.

 

Oil can be found in the air filter box for the simple reason that the airbox is connected to the engine via a pipe and the oil vapors are sucked into the combustion chamber.

 

Yes, absolutely normal. If I didn't find that oil at the base like that I'd be concerned that the filter didn't get oiled before installing. Foam filters must be oil wetted. They do not run dry. The oil on the foam is what collects the dirt/dust from the air taken in. Some oil at the bottom of the filter is absolutely normal and it will get on the mounting surface.

Clean clear oil like that on your finger is oil that has drained down off of the oiled foam of the air filter. Oil from the engine would likely be darker.

It is not unusual to have oil drain down through the oil wetted foam and is nothing to be concerned with. That's pretty much what my filters looked like on my KLX250 and 650 after use. Clean it and if it's not deteriorating in the process oil it up again squeeze out excess oil and reinstall it.