I agree with Exaviator. Always check the end gap. If the cylinder is worn, the ring gap might be out of spec, in which case, you need to bore the cylinder and fit oversized piston and rings to match. The end gaps on new, standard size rings are set to match a new cylinder, but will work in a used cylinder, as long as the end gaps don't measure out of spec in the cylinder.
Most 4-wheeler problems are caused by a loose nut connecting the handlebars and the seat!!
You only need two tools in life -- WD-40 and duct tape. If it doesn't move and should, use the WD-40. If it shouldn't move and does, use the duct tape.