This is on my buddies 06 yz450. He bought it used and since he got a smokin deal on it, he took it to a shop to get it checked out. They checked the valves and did a few other things. They said the bike had very low hours and was in incredible condition. So on his first ride, we notice a bunch of oil all over the left side of his bike. We figured the shop over filled it w/ oil and that was it. 2 weeks ago, we did a half day ride and it continued to blow oil out the breather tube coming from the valve cover. I took it back to my place to check it out and drained the oil. Less than a qt came out. I changed the oil filter too and it was chard black. So I thought maybe that was the problem. I put a new oil filter in and put just over a qt of oil in. This weekend I went to caineville and sure enough, its spitting oil out of the breather tube again. I let it sit for a couple min and took out the dip stick and oil began to come out. Not much, but enough to pour out the top. I'm pretty sure I didn't over fill it when I changed the oil since I checked it 3 times. The compression feels good and everything else looks brand new. What can be the problem causing it to spew all its oil out? I mean it will empty the case if I let it.