If it is backfiring in the exhaust. You must have fuel in the pipe to ignite. The timing could be way off too. As you stated it was way advanced intial, right. Check the balancer and make sure that it hasn't slipped. You can check it with a piston stop and see if TDC is correct.
Check power valve for leak.
How are the plugs running??
You maybe alittle too rich, causing the raw fuel in pipe that EXPLODES. Float level to high too.
|