Please help - 50 SX Pro Junior Won't Start
Hello and thank you for reading this post. We have a 2002 50SX Pro junior that ran like a champ. My son rode the bike - shut it down and then it would not start. The symptom appeared to be a loss of compression or something broken in the kick start because the was ZERO resistance when you cycled the kick start. So here is what we have done:
1. Removed the case and checked the kick start assembly. Everything appeared to be in good working order and all parts are present. No obvious missing, broken, or even damaged teeth on any gears etc.
2. Removed the spark plug - as soon as we removed the plug and cycled the kick start we got resistance and the thump thump. Replaced the plug with a new one and discovered as soon as the plug was in - no resistance or thump thump - when removed - we got both.
3. Removed and replaced all top end components. Honed the cylinder, replaced all gaskets, piston, and ring (clips, bearing, etc.). Put it all back together and same thing. Pulled the case cover off again and I just don't know what is wrong. I can feel the piston move through the exhaust port when the kick start is cycled. But as described below - not every time.
So here is where I am - when the kick start is cycled - it does not rotate the crank or piston every time. About every 4th cycle I get the thump thump. Obviously there is something wrong - but I have no idea where to start. Any help would be appreciated. Thanks D