picked this up cheap last year ,got it for the kids to use works great out of the gate. starts real easy and works good cold but after you ride it for a half hour or so it heats the plug on clutch side and starts loosing power. Check plugs and the one of them is really hot ,have tried hotter plugs still does the same. if i put a new plug in start it up and go again for another bit but trouble keeps recurring. Have adjusted the needle in the carb up and down ,does anyone have any suggestions ,thanks