I will start by saying this machine came to me not running. It had been overheated and the piston was scored. Disassembled, replaced piston and repaired cylinder. Overhauled the carb with all new parts. Went to start and machine would not run unless the choke was used. Went thru carb again. Replaced both pto and mag side crankcase seals. Machine will now run pretty good. The problem I have is when letting off the throttle there is a tremendous backfire. I have checked and double checked for air intake leaks (lean condition). When the flywheel and stator where removed everything was put back into the original position. How do I check timing? Would this cause my problem? Do not know where to go from here. Any help or ideas would be appriciated.

 

welcome to the site. my guess is if the timing were off it really wouldn't run right at any time. if the bike wasn't running when you got it becuase of a lean seizure. you need to find out why it went down. is the getting stock or was the carb plugged up? were the seals bad?

 

I believe the cause of the melt down was the mag side seal. When I replaced the seal it came out with the lip of the seal torn loose. The machine would not hardly run and then would not run after the rebuild. Replaced the seals and the machine runs good with the exception of the backfire.

 

Try raising the needle in the carb a notch at a time , this will give it more gas, if you run out of needle you will have to go up one size on the main jet.