Are you sure its not gas, thats backfiring out of the carb? this happens when ur timing is advance Waay to much like 40+ the funny thing is if it starts it will run, just wont start sometimes. Only other things i can think of are choke not opening at all when its hot. try to pin it open all the time with bailing wire or something. mines been like that for 2 years and works fine. Also could have something to do with ur thermo sensor on the intake. thats my
