2007 trx crank case is pushing oil in to air box

I have a 2007 trx 400 ex and I just bout it. The kid said it was just ringed. I got it home and was going to clean the card and all that good stuff. I took the air box lid off and noticed the bottom of the box was full of oil. So I cleaned the card the air filter and the hoses rode it and it filled back up. I talked to a mechanic.and he said it could have been from putting to much oil in it but it always reads that its low so its not over filled. Any suggestions on what it could be or how to fix it?

Run for ten mins, then check oil. betya your over filled.

he said it wasn't over filled because he checked the level and it always reads low. Gotta the read the whole post marco.

Wipe it all clean in the airbox, then run it for awhile and see if it still puts oil in there. Are you sure it's motor oil and not the filter oil? if you find oil in the airbox again then you do in fact have blow by. Does it smoke at all through the exhaust when it's running?

Re-ringed dont mean squat if it wasnt done right. The cylinder needs to be deglazed and checked for out-of-roundness. If its pumping that much oil in the airbox and its showing low on the dipstick i bet you have blow-by on the top end