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Thread: 400 EX (426) rebuild carb/ fueling issue

  1. #1
    Join Date
    Jun 2009

    400 EX (426) rebuild carb/ fueling issue

    Hey guys, I'm looking for a little help. I have an 07 400EX that I am getting back together after sitting for a few years. The bike was rebuilt before it was parked and only had 1 ride on it. I am in the process of just cleaning it up and getting her running right. I replaced the carb with a new one and have read a ton of threads on where to start on the settings but I can't seem to get it. It has a 426 kit with stg 2 hot cam, stock airbox with moose foam filter, 42 pilot/ 175 main/ 2 1/8 turns on the A/F screw. This thing will fire right up and idle just fine, and blips the throttle but if you give it too much throttle too quick it will just die (you can play with the throttle to try to get the revs up but it misses like crazy and will eventually die). I am heading to the shop after work to get a few main jets to try but any thoughts as to which way to go from the 175. I cant seem to find a definitive answer but I am thinking too rich and needing a smaller jet?? I cant get it out to ride it to fine tune it and do a plug chop.

    Possibly related= the choke lever seems to have no impact on or off and it will only run (idle) with the fuel on reserve. I understand the petcock would seem clogged, but I had the tank off draining the fresh gas and it runs fuel in both positions and stops at "off". That has me stumped.

    Thanks for looking and any help you can provide.

  2. #2
    Join Date
    Apr 2005
    youll have to drop your needle down (raise the clip up on the needle when the point is down). try moving it 1 position and see how that goes. it is out of the pilot circuit if you are hitting the throttle a bit, the main doesnt open all the way until the needle it out of it. 3/4 throttle to full throttle.

    if you can get it running long enough to warm it up all the way and do some plug chops, you can tell how your main jet is, then work your way down from there with different areas of the throttle and killing it. be prepared to destroy a few plugs though.

    2019 Maverick X3 XDS Turbo R
    2003 TRX 400EX

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