Oil leaking out of air box

I bought a 2007 CRF250 about a month ago and got to ride it for the first time today. When I started the trans and engine oil were at the proper levels. After about 30 minutes of riding the bike started to smoke pretty badly and there was oil all over the swingarm that was coming from the airbox "drain??" When I go home and checked the oil levels the trans oil was very low and the engine oil level was really high on the dipstick....like I had added about 1/2 a quart of oil to the left side. Is this because of a crankshaft oil seal on the right side? Appreciate any advice.

Thanks!

Yes

And might be the left side balancer seal.

 

Search oil migration in the CRF250R forum

Check the balancer bearings too, if they are starting to go bad that can be what causes the seal to leak. The good news is you dont have to split the cases or take the flywheel off to fix it.

The right side crank seal was bad.  Not sure what caused it, but I'm finding all kinds of creative ways the previous owner "maintained" this bike.  This is my first 4 stroke so i'm learning a bunch of new stuff.  I rode 250 2 strokes for several years before.  Thanks for all of your input.

I have the crf 2008 450r and found just a tad bit of oil and gas mix in my air filter box I just wiped it out with a rad it wasn't a lot tho

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