I've had my king quad for eleven years and never run into this problem. It starts great and runs great for about five minutes. As soon as I go to take off, it sputters and dies if I don't drop back to idle. It will idle fine after that but basically won't go anywhere. It acts as if there is a restriction in the fuel lines or something like that. I did find one blockage in the main fuel line from the tank, checked all vaccum lines to carb, and changed the spark plug. Plug was basically clean and not majorly worn, just fuel washed. It's got the same oil leak at the head it's had since 2002. Nothing else has changed. It's the middle of deer season and I've got to have my quad up and running! Any thoughts?