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Thread: yet another jetting question by a newbie

  1. #1
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    Question yet another jetting question by a newbie

    I just got my k&n jet kit today and have started my first attempt at jetting my 400ex. My only mods are a k&n filter with outerwear and a WB slip on exhaust. Airbox lid is on with no holes drilled (yet). I followed the stage 2 directions that came with the kit and redid the needle valve to the third notch and put the washer on top of the e-clip. I jetted to a 170 and that didn't seem to be right so I worked my way down to a 155. I seem to be having the same problem with every size. The quad will idle fine but when I rev it up into the higher rpm's it seems to start cutting out. I noticed when I changed the jet it didnt seem to be seated in the bowl straight. I did not cross thread it or anything it just seems to be sitting in there crooked. Is it supposed to be seated crooked? What is causing it to cutout at high rpm's? My stock jet was a 148 and I've tried all the larger ones with no luck. Can someone with a similiar setup tell me what their settings are. Sorry this was so long!!

  2. #2
    Join Date
    Jun 2001
    Location
    Dallas, TX
    Posts
    1,762
    Sounds like you are rich. With no air box mod (no lid, holes, etc.) you need to just run stock jetting or possibly one size up. You simply can't get enough air with the box closed up. I have the same setup as you, but with a 2 1/2 hold in my lid and 160 main jet, second clip from the bottom on the needle and 42 pilot. It runs great with this setup. You will be very pleased if you get some more air into your system. To test it out, take the lid off and go for a ride and see if it improves (be aware this may cause you to run lean, but it should act different than it is now, which should lead you to the answer you are wanting).

    Also, my main jet is off-center as yours is, so I don't think it is a problem. Good luck.

    Here is a picture of what Gabe (one of the most knowledgable people on this board) did to his air box lid. I did a similar thing after seeing his and it works great. If water gets in, it just slides under the filter and out the hole (have to take off the plug). http://home.earthlink.net/~gellett/airbox_mods.htm
    Last edited by Razorback; 08-29-2001 at 01:36 PM.
    2001 MX Race 400EX - TQRA Series Racer #721

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  3. #3
    Join Date
    Apr 2001
    Location
    Bethlehem TWP., PA
    Posts
    163
    Make sure to run it under a load or you could be hitting the rev-limiter.

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