what do i need to do

[yellow400ex0102]

i have a 400ex and i have a t-4 pipe with a k&n air filter. when i like pucnch the gas it backfires or cuts out does any one know what i should do? thanks

[Wired]

REJET would be my guess. whats your current jet settings? when i had my stock engine with a new air filter and a t-4 exhaust my jetting was pretty damn good at a 38pilot and 165 main and the needle on the 4th position.

[RIKR4X]

what is your jetting? Does it do it at the burp of the throttle or the full wot? try your air fuel mix screw.half turn out.

[yellow400ex0102]

i have a stock jet in. i will try changing it but what should i change it to

[honda 400ex 69]

dude didnt u have a jet kit what happen to that? lol im jk


he is running the dyno jet kit needle on the 3rd spot and a stock main jet(i broke his dyno main jet adabtor so he cant use the jet kit main jet) what size mainjet should he get? like a 155?