usually when that happens on a quad it is becuase the idle is set just low enough for it to carbon up and die. OR it could be getting too much fuel and flooding out. Once you let it idle off and die, pull the plug to see if it is wet or just normal looking...
If it is wet it is getting too much fuel and you will need to adjust the carb accordingly. If it is still dry and looks normal, then the idle may be set too low. What does the exhaust smell like? Kinda like it is running rich or too much carbon??
AirBorn!!
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