Jetting Help Please!

[WittmerA]

I have a 400ex with stock header pipe, stock air filter, and stock jet settings. i purchased a HMF slip on and want to know what kind of jetting i should do to it. Im also looking for a K&N air filter so hit me up. any info would be very much appreciated!

[RIDEREDson]

a 146 main should get you close.

[Rkangel7]

I have a White Bros. slip on with K&N filter. I'm running a #150 main jet with the stock 38 pilot. It seems to be pretty close for my riding locations. Although, I would recommend going up on the pilot (which I'm currently doing). The 400ex is already cold blooded. Moving up to a #40 or #42 pilot jet will help cold starting issues.

[BEAVER.989]

I'm running a 152 main, 42 pilot, stock needle position and 1 1/2 turns out on the fuel screw with an HMF slip-on, Sparks filter and choke removed. It seems pretty darn close to me.

this can't really be answered for you...go here:
http://www.jetsrus.com/FAQ_jet_kit.htm

and read up....