check the plug pull it out ground it kick it over to see if you get spark if not try a new plug or clean it off see if that works if you have good spark clean the carb out w carb cleaner get the stuff with the red tube like wd40 has it makes a defrance being able to blast them out must be CLEAN !!! one grain of fine sand or dust can make it not run properly if at all make sure to get evry hole or jet ect and take apart the main jet to just do it all at once and remember how it gos back together!!!!!!after that tune the air screw to around 2 in a half to 3 turns out take it out and bump start it if it dosnt start from kickin over.