hello everyone, I recently bought a yamaha moto 4 225 for my wife, and the first time we took it out I noticed that it sounded like the motor was starving for fuel under full throtel and would not stay running when hot.
I rebuilt the carb and put a bigger main jet in it which fix the problem of fuel starvation, but when the motor gets hot it will back fire through the carb, wont stay running and wont start. Sometimes I can get it running by spraying starter fluid in the carb. reving up the motor it runs fine. I think its a timming issue, but I,m not sure how to check it or adjust it.

 

If this is a 4 stroke, have you adjusted the valves?