I found a 06 yz450f with a siezed motor. I can pick it up for $900. I went and looked at it and when I pulled the oil filler plug I found it to be out of oil. Obviously I can't say how bad the damage is but it is a otherwise clean bike. The guy said he had just had the clutch and gearbox done at a shop. He said it's not worth him fixing because he would have to have a shop do it. I on the other hand can rebuilds the entire engine myself. What is the best and worst case scenario and is it worth the risk?