choking

[vapor400]

I just got my '03 400ex.It is stock and I am new to the sport. My bike stalls out when i accelerate too fast if i am going and then thumb the gas hard it chokes out and stalls. If i accelerate gradually it will still go to full speed. Any ideas for me? I am thinking jetting is not right or air filter isnt good not eough air to gas? Appreciate any thoughts on this.

[Chino886]

Originally posted by vapor400
I just got my '03 400ex.It is stock and I am new to the sport. My bike stalls out when i accelerate too fast if i am going and then thumb the gas hard it chokes out and stalls. If i accelerate gradually it will still go to full speed. Any ideas for me? I am thinking jetting is not right or air filter isnt good not eough air to gas? Appreciate any thoughts on this.

sounds like you definitely have a jetting issue, not your pilot jet but your main....

[F-16Guy]

Originally posted by vapor400
I just got my '03 400ex.It is stock and I am new to the sport. My bike stalls out when i accelerate too fast if i am going and then thumb the gas hard it chokes out and stalls. If i accelerate gradually it will still go to full speed. Any ideas for me? I am thinking jetting is not right or air filter isnt good not eough air to gas? Appreciate any thoughts on this.
Is this when the quad is still fairly cold, or all the time? The 400ex is very cold blooded until you re-jet it. If it's just in the first five minutes or so of riding, then I would go to a 40 pilot jet and a 150 main. That should help you out a little.
Also, make sure your air filter is clean. If it stalls out when it is fully warmed up, it may actually be starving for air, which would cause it to be rich and run like crap.

[h400exrydr]

mine did that too...i jus took out the choke. but wat it is, is the detent ball, i read it in a dirt wheels magazine, there might b a spring or somethin too, not sure bout taht tho. hope this helps

[400exstud]

If I was a betting man I would say its a bit rich. Main jet that is.