Upgrading My 400ex

[Meyer96]

I'm getting ready to do some engine work to my 2004 400ex. I just bought a Stage 2 Hotcam and 426cc piston with 11:1 compression. I'm also going to have the head ported. I was wondering if anyone had any idea on wat jet i should run with all these upgrades. Any help would be great?

[honda400ex2003]

178 main, 42 pilot, 2.5 turns out on the f/a and 3rd notch on the needle of your 400ex carb will get you started. welcome to the site, not to sound mean or anything but find the search button quick. when your first post is what is my jetting for a 426 you can use it quite a bit. It has been beat to death by many before you. lol. good luck you will most likely be running a bit rich on the main, my suspicions are that it is going to be around a 175. just a quicky since there are many many variables that go into this that you have not listed. you will enjoy your machine when you are done. steve

[JOHNDOE83]

Do some reasearch on jetting before running the atv after the big bore install, there is 416ex guys with 205 main jets on here.

I use a 220 main jet in my 440ex.

[honda400ex2003]

if you decide to use a 450 carb you will be in the 200s if not you will be run about 175-180. steve