My cousin just bought a yfz450 '04 model. When you hit the gas it stalls(everytime). He tried a jet kit, didn't fix it. I took the cover off the right side of the carb and tightened the spring on the pump arm,didn't fix it. Valves check good and runs real good after it gets going. Anybody seen this? He's ready to sell it and get a Honda! It's a good bike other than that and I hate for him to get mad at it. Thanks.

 

what jets are in it now? is it piped? is the airbox lid removed?