I recently cleaned up my old fourtrax for my son and I took apart pretty much everything and replaced the stator and cleaned out carb twice and cleaned out gas tank and cleaned out all the fuel hoses and replaced air cleaner. I did get it to start for the first time in 5 years after doing all of this to it but it had like a burn plastic smell to it and then eventually disapated and ran like a champ . But after running it for two days straight I turned it off using the safety cut off switch located beneath the left handle grip and ever since then I could not get it to crank back up . I took apart the carb cleaned it and drained the gasoline again and took the crank case the altenator (stator cover) apart which looked a little worn but still was creating a spark when I put it all back together. All it does now is makes a small back firing sound and shoots gas out of carb into air cleaner area. If someone could please help me out so my little guy can go out and have some fun in the mud.