There should be a small hose connected to the bottom of the airbox. This connects to the engine and is where the engine expells excess moisture. (like the water that separates from oil) If the quad has been ridden off camber, stood up on it's grab bar, or rolled over, the there's a chance some oil made it's way up this tube and into the airbox... It shouldn't be cause for concern... (unless there's a lot)

 

Well, when I cleaned it up after initial purchase, I cleaned the filter too. I checked it twice yesterday after riding and it was dry as a bone. It had been flipped as the previous owner told me he had it in a drift and dug the left rear tire... hence the damaged floor board cover I am having to replace.

I swear, with the exception of it not running 100mph (BIG LOL... I am gonna hop it up some... shooting for 65 mph, we'll see), I am tickled to death with this quad in every aspect. I had a mechanic buddy over last night and he rode it. He brought it back and told me it was good to go.