400ex jetting with an HMF full system

[400exstud]

Don't flame me for not doing a search on this because I checked the first 15 pages and couldn't find the right thread.

Alright I just ordered a HMF full system and am running with a K&N + outerwear, and the air box lid is ON. I ride at about 1,000 ft above sea level.

On the HMF sight it says to run a 200 main jet but that seems WAY too rich. Where do you think I should start with the main jet?


PS: How will my 400 with this pipe compare to my friend's stock Z400?

[MadMax27]

No No No, Noooo 200. With my lid on, 180 is a tad bit rich, but Im comfortable with it that way, Never a Fear of it bein Lean. I also swapped out to a 42 Pilot while I was in there, Neither their site or directions made note of that. It will most likely need it. My neighbor has a new Z400, and the other a Raptor, I hang with both of them just fine. For full on drags, with my gearing, Ill stomp a Z till 4th, then he'd catch up and just start to move out in 5th. The pipe makes awesome low-end. Which is why I got it. Im sooo glad I ditched my T4 for the HMF.

[400exstud]

Thanks for the reply. It sounds like I am ganna have a lot of fun this summer!

[2001400exrider]

im runnin 175main, needle clip second postion from bottom and 2.5 turns out of air fuel screw...wondering if i should swap in a 42pilot jet for some more low end..(1/4 throttle) iam also about 1000ft above sea level

[400exstud]

Once the pipe arrives I am also going to start out at a 175 main jet and go from there.

[meanyellow03ex]

I have just the slip on HMF and run a 170 main with a pro flow intake and filter and a Powroll vented lid. It was dyno tuned and found the 170 to be optimum. Many may say that 170 is too big but the #'s show otherwise and it runs great. With the full system with lid 175-180 is probably correct.