So I picked up two used raptor 80s for my kids. One rides perfect. The other just started blowing grey smoke. We went on a trail ride today for a few hours and it smokes like a champ. Then i see oil coming out of the muffler. Im guessing its the rings allowing the oil to pass causing the oil in the exhaust. Any opinions? Would it be better to replace the piston and rings or the whole motor itself?