Just went to a 127 1/2 main jet. Thing will really get up and go, also did the airbox mods, and removed the spark arrester. It still backfires every once in a while when I let off the gas. What does this mean? Is my mixture not right, went 2 1/2 turns on the mixture screw. It won't take any choke, it just dies when I try to give it choke. I was debating if I wanted to do the rejetting now because it is so humid (70% humidity and 95 degrees) but I think I'm okay, I just need a little adjustment on it, like I said it's got more take off power now and it's got more reserve power for the big mud holes.

 

if it won't take choke without throttle that means you should turn the screw in about 1/4 turn or a 1/2 turn..whatever it runs best at..that should also stop the backfire