My 87 quad is down and doing some work to it right now. There was some knocking in the chamber and my brother said it was piston slap. Doesn't sound good to me but has anyone had the same problem and where to go from here? My quad is down and I want to fix every problem on it. When it is running and you touch the head you can feel the knock of the piston. Also when I changed the oil I had some silver from the clutch plates in there but don't think this has anything to do with it.