I have a 00 400 complete Big Gun exhaust, KN Filter + power kit, needle in middle groove & 155 main jet. My bike was running too rich, so i went back and read the jetting directions that came with my exhaust. It said to take the lid off the airbox, so i did. Now my problem is sometimes it wants to bogg down mainly between 1/2 to 3/4 throttle. I mainly notice it when im climbing hills in 2nd or 3rd i go to give it alittle more throttle and and she starts to bogg and i have to clutch or down shift to make it to the top. When it was stock it had no problem doing this up a hill. Is it gettin too much air & not enough gas? Should i move up another main jet to get more gas? My plug seems to be burning normal (a light black). Ive seen on here where people are bumping up the pilot jet, where would that show improvement in the power band. Any info is greatly appreciated!

 

BG400,
here are the three jets & the segments of the band where they function:
pilot jet: idle to 1/4 throttle
needle jet: 1/4 to 3/4 throttle
Main jet: 3/4 to full throttle
There can be some overlapping in these areas, but only slightly.The pilot would have no effect at the range you mention.It sounds like you need to raise the jet needle one notch. with your plug being black, that would indicate you're too fat on your main. The plug should be a chocolate brown immediately after running at 3/4 to full throttle. Plug reading isn't as good an indication of proper jetting as it is on 2 strokes due to the absence of oil in the mix. In other words, anything other than medium brown indicates a more pronounced leanness or rich condition in a 4 stroke.
If I were doing the jetting I'd raise the needle one notch and test ride at 1/4 to 3/4 throttle in whatever gear for performance & then at 3/4 to full for 1/2 mile or so, then shut down immediately without any idling . Pull the plug.. if it is still black, drop one size on your main & retest.
Unfortunately jetting isn't an exact science like mathematics, so changing only one thing at a time & testing is the way to go.


------------------
THE AZ HARD PACKER, calmiller@kachina.net

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[This message has been edited by hot_shoe_cv (edited 12-07-1999).]

 

BG 400
That's a strange one.Here's my settings.
Pilot jet-42
needle on third notch.
Main-170
Stock filter
Holes in the air box lid.
And running great.
Try putting the air box lid on with the back clips under the lid and the front clips cliped on, And test.

Check hose from carb to motor?

If that dosen't work.Put the needle to third notch and up the main to 160,And test with air box lid setup.

With the holes in my air box I can still feel some vacume at higher throdle.
<a href="http://home.earthlink.net/~gellett/400ex/">LRDpipe</>

[This message has been edited by trx430ex (edited 12-07-1999).]

 

What/where is the needle jet on the 400EX carb? I know what/where the main jet is. Is the needle jet what the main jet screws into? The shaft with the "holes" or "notches" in it that you can pull out from the bottom bowl drain plug?