My ATV was stolen and recovered in terrible shape. I am trying to rebuild the bike. i am to the point where i can get it started, but the is very low power and alot of smoke and oil blowing from the exhuast. At first I was going to do a valve and ring job, but this is what I found out.

the air breather was full of oil. There is a hose the goes from the bottom of the air breather to a nipple on the top of the crankcase. I removed the hose from the top of the crank case and ran the bike. oil was constantly coming out of the nipple until all the oil was gone.

can someone tell me what the purpose for this hose from the crankcase to the breather is for?
why would oil be coming out of the top of the crankcasse like that?

My feeling is it is a signal that perhaps the oil filter is clogged or something?

 

sounds like the positive crank ventalation hose....if you are burning oil this would answer the filter situation...hope this helps

 

thinking about it a little more....the theives might have been mixing the oil....so you may not have ring or valve repair to do....glad you got your bike back though...some never do...

 

What it sounds like is the rings are shot. The compression is leaking past the rings and pressurizing the crankcase, causing the oil to blow out of the crank vent. Theres not really any other reason for the oil blowing out other than this. If its using alot of oil, I believe I would tear the top end down and check things out.