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Thread: 400ex jets

  1. #1
    Join Date
    Dec 2011
    Location
    ga
    Posts
    7

    400ex jets

    im going to rejet my 01 400ex and i pulled out the jets and realized that the main jet was a 118 and it has the keihin logo on it so i assume its keihin brand but online it says stock size is way bigger?? what do you think also the pilot jet is a 38 thanks
    400exrider

  2. #2
    Join Date
    Dec 2011
    Location
    ga
    Posts
    7

    .

    here are the mods if this helps
    k&n airfilter with precharger
    ground down header welds lexx slip on
    on the intake boot (carb to motor ) i ground down the boot to match the intake on the head and sanded it smooth
    the casting marks are removed and poliched up in the intake side of the head! thanks again and what shoul my jet sizes be?
    400exrider

  3. #3
    Join Date
    Oct 2012
    Posts
    148
    i'd try a 155 and a 42.. the 42 just makes it start easier in the cold, and controls the idle, the main controls the amount of fuel over 1/3 throttle
    i replace all my gas petals with on/off switches

  4. #4
    Join Date
    Dec 2011
    Location
    ga
    Posts
    7
    why is there such a small jet in there now though? 118???
    400exrider

  5. #5
    Join Date
    May 2010
    Location
    Moline, IL
    Posts
    237
    it's more than likely a 148, not a 118. Look a little closer...stock is 148/38
    2007 TRX400EX Sold & missed!
    2014 Polaris Sportsman 570 (awesome 4x4 quad)

  6. #6
    Join Date
    Dec 2011
    Location
    ga
    Posts
    7
    thats what i thought to and its a 118 cus a while back b4 the mods i replaced it with a 148 and it ran like shi* then i cleaned the old jet and it was a 118 so i replaced it with a 118 and it ran perfect but not it needs rejeting
    400exrider

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