Try this i had the same issues with my bayou ..there is a rubber o ring gasket behind the intake manifold in between the engine . i got a new o ring at ace hardware 85 cents .it was sucking to much air causing it to backfire. No it runs fine plus i turned in the air mixture screw out one turn . ......try itMaxload, have you discovered a fix for this? I have a similar problem. After having the carbs professionally cleaned it will now run with the choke off once it gets warm, but I can't give it any throttle without it backfiring and losing power. Seems like a it is starved for fuel, but I have opened up the fuel mix screw and it hasn't helped. My muffler is completely rusted out, but I can't image that would cause it to run as poorly as it does.