stumble at low throttle

[flaneledholes]

I have just went out and bought a 400ex and the only motor mods it has is a k&n filter.Air box and everything is the same...Im pretty sure it was jetted for the k&n cuz it does not backfire... Is it natural for it to stumble and act like it is cutting out at low throttle when you are really luggin it????? I mean I cant even lug it in 2nd gear...But first gear is fine...

I'd have to say you gotta jetting issue bub..:(

[flaneledholes]

In my main or m piliot??? Can it be solved by moving the needle clip up a notch???

[flaneledholes]

Hey what if I remove the s/a will that help????
Bump...

[flaneledholes]

I removed the spark arrestor and it leaned it out so it is runnin great now...