I was in the process of doing a top end on my 04 CR250 and after talking to the owner of Moto-X-Perts in Lafayette, (IN) about how I have alot of oil coming out of my pipe and that I am fouling alot of plugs he informed me that my crank seal is leaking. I already suspected that was the problem but how do I know for sure thats what it is? After draining the oil in my bottom end and pulling the engine out of the frame I got a good look at it. The oil in the bottom is black but looking down inside the crank from the top end there is no black oil in there at all. I would assume that if it is leaking into the top end there would be some visible black oil in there?