So I have a 1990 Cr125r I replaced the piston, ring and gaskets. The bike started on the 5th kick I let it run for a couple min. Then shut it off I kicked over the first time. It didn't have much fuel in it and it high Reved it's self when it ran out. Now it won't start at all I ripped the head off and every thing seemed fine cleaned the carb and all it does is backfire while kicking over at full throttle. My friends and I think it's the ring because the compression feels light. some input and ideas are greatly welcome.