studder in 2nd

[RACER_XXXXXX]

:confused:

i am having uble whith my friends 400ex it has a k&n filter with the lid on and a big gun full race system and it has a 170 main jet.
the problem we are having is that when u gun the throttle it starts to studder at high rpm's ,its the worst in 2nd, but if u gradually ease into full throttle it wont studder. also there is no studdering in neutral when u rev it. any advise will help ,thanks

[cals400ex]

put a keihin 155 mainjet in and you should be good to go.

[RACER_XXXXXX]

ok thanks

[promisc]

Way to rich! i run a dyno 160/165(winter) WITHOUT the lid. Try to let the 170 in it and remove the lid. Decrease the mj size until you get a cool light brown plug. Or let the lid on but drop below 155.

[TravEX]

Originally posted by RACER_XXXXXX
:confused:

i am having uble whith my friends 400ex it has a k&n filter with the lid on and a big gun full race system and it has a 170 main jet.
the problem we are having is that when u gun the throttle it starts to studder at high rpm's ,its the worst in 2nd, but if u gradually ease into full throttle it wont studder. also there is no studdering in neutral when u rev it. any advise will help ,thanks
take the lid off!!! or get the EHS Racing lid withe the outerwear!!!