400ex newbie question

[juddts]

Hello all, I am a newbie and need a little direction. Just picked up a 2001 400ex with 440 big bore kit, HMF Q exhaust, and foam filter. I cannot get the quad to idle/run correctly. Once started the motor will run okay but once you blip the throttle it will backfire and usually die. When I put the choke the entire way on it runs great at both idle and at WOT. I really don't know much about small motors, I've always had jeeps and such. Any help is appreciated.

Thanks, Judd

[04blasterkid]

um if it runs good with the choke on, it sounds like its really lean, check the plug and check for cloged jets

[thisperishedmin]

sounds like it may not have ever even be setup to run with the big bore.


if it runs good with choke on that means your starving for fuel (aka lean like said above)


Take your carb off and clean it up...if your still facing the same thing youll wanna start rejetting, go bigger on the main and pilot jets...



If youve got a few bucks to kill everyone around here seems crazy about the 450r carb swap, may be worth looking into? good luck!

[dariusld]

I would take the carb apart and see what jets are in it and go from there. If you don't know anything, we can help. While you have the carb off, might as well clean it. Have you cleaned the filter?:::

Just because everyone says its your jetting doesn't mean its your jetting, could be alot of things.

[juddts]

Thanks guys, appreciate the responses. I am new to this and need all the help I can get. Are there any good sites for jetting procedures and other info? I've done a search but haven't found much... thanks again, Judd

[Eviltanker]

Look in the how to section.



Maybe this will help

http://www.exriders.com/vbb/showthread.php?s=&threadid=221872

[juddts]

Awesome, thanks for the help guys. Judd :)