Ok a little history....A screw got sucked into the carb somehow, and the piston mashed it into the head. Pulled the motor apart and the screw did not contact a valve, and the piston was damaged on the flat area not on the sides. Now it's put back together just how it was, with the screw removed. Yes, I know...cheap. Besides the point. I figure it will get a hot spot and eventually need a piston, but when it went back together, it ran like a champ - burns a little oil, but not a lot I dont think. Well, I sold the quad to a friend who is the one that put it back together and has been riding it. It got low on oil and is now making a rattling sound. I'm not sure if the oil being low caused it, or if it started happening a little while after or what. All i know is that it got low on oil at one point, and now its rattling also. I'm buying the quad back from him this weekend - the deal is just too good to pass up. He has been riding it occasionally, and its been ridden hard. The rattling is semi quiet at idle but gets louder and consistent when it gets hot. The rattling sounds like its coming from the right side of the motor, near the bottom. Any ideas? My plan is to ride it until it doesnt run anymore, and then fix it. Unless perhaps its something easy? I don't want to buy it and tear right into it, because im too broke to fuck with it right now, but I do want to ride it a little bit.