Jettin Help !!PLEASE!!

[ohsobad_chevy]

I have a 2004 honda 400 EX, currently it is stock. I plan to put a HMF sport series full system exhaust, Uni filter (without airbox lid), and rejet my carb of course. I live in Oklahoma, where the elevation is approx. 715 feet above sea level. I cant seem to figure out what size main jet i would need for the correct mixture. Please let me know the correct way to figure out what jetting i would use and how to test my configurations. Any help is greatly appriciated.
Thanks fellas,
<Mat>

[YFZ450CW]

Well im not to familiar with the 400ex but you can give hmf a call and ask them they will know. Also with my whitebrothers they sent me jets to use.

[2004exrider]

with my slip on they sent me a k165 jet, so im sure they will send you a jet or two because when i ordered mine they asked where i lived and stuff. but if they dont, go up to a local dealer and start out with like a 170, 175, or 180 just grab those 3 jets and return the unused.

Jimmy

a 42 pilot and 170-180 main will work mint.

[rneal]

140-142 kehin pilot
155-165 kehin main

HMF's recommended sizes are on the rich side to protect themselves.

If your not installing a cam, I'd consider running the srock headpipe with an HMF slip on.

[2001400exrider]

im runnin a k175 main, 3.5 turns out on fuel screw, 2nd postion from bottom on needle. perfect jettin dude. i started at 162main WAY TO LEAN, PURE WHITE PLUG, then went to a 170, still plug was greyish/white, then i went to a 175main, did a plug check and the plug was perfect tan brown:D and now she hauls ***!

[2004exrider]

^^^ yeah, no need for a full exhaust if you have a stock engine (unless your plannin on building it) not really any noticable power gains from what i heard. might sound a little louder though. the stock header isnt really thhat restrictive, a lot of people just take it off and grind down the welds inside of it.

Jimmy

I like burning my self on my aftermarket header. not having a little gard there is fun fun fun.

[YFZ450CW]

Originally posted by mittimj
I like burning my self on my aftermarket header. not having a little gard there is fun fun fun.

HAHA thats also the main reason i opted for a full system rather than slip on. although it has gotten me to not ride without my boots and a pair of pants:D

[MadMax27]

I have that pipe. For me @ 315 ft above sea-level. a 172 Main. 42 Pilot, and clip 2nd from bottom. With snorkel removed, and 2- 1" holes in lid, Im finally tan. I put tight screen mesh over all holes, dont want larger debris in their. Also running a UNI filter. I also run the quiet core, 175 would prolly be good if its removed....

[ohsobad_chevy]

You guys are great, ill have this baby runnin' great before too long. I hate the 2 week wait at HMF though. Good things come to those who wait.
Thanks fellas,