I went to look at a 2004 Honda Foreman 450 today and the thing was blowing oil out the exhaust pipe.It had been bored out and over sized piston and rings installed.The guy didn't have the head done and I am wondering if that could be the problem.Blowing oil out by the valve seals perhaps.He said it worked good for the first six months and gradually started blowing more and more.Any thought on what the problem might be?