Jetting...

[DH400EX]

I have a '99 400ex wit a Pro Circuit T-4 slip on, and im goin to get a UNI air filter and was wonderin what size main jet i should get. I was thinkin somewhere around a 160 or 165?

[Mobile Dyno]

If your motor is stock, I would do the 160. I would do the 3rd clip from the top on the needle and 2.5 turns out on the mix. screw. :D

[DH400EX]

ok, thanks

[04'400ex'er]

start with a 42 pilot and a 155 main. Im thinking a 158 will do the trick and a 160 would be the largest possible.

[whoamack22]

ok im havin same prob as dude except i have a 416 with 11:1 piston stage 2 hotcam , power bomb header with hmf slip on, what should my main jet be ?

[04'400ex'er]

Id say 162 to 168, depending on temp. and elevation. jus buy a few mains and try them out. it only takes 2 minutes to change one out on the 400 anyways.

[whoamack22]

ok well the hmf is on the way, i just got this bike and it has the stock pipe on instead of the hmf and it dont feel like a 416 really, i mean i dont know im hopin having a true exhaust will make a difference to it

[prepracing]

go to HMF website, they have some jetting specs if you are using their pipe

[DH400EX]

Originally posted by Mobile Dyno
If your motor is stock, I would do the 160. I would do the 3rd clip from the top on the needle and 2.5 turns out on the mix. screw. :D
i did all that and when i rode it today, when i let off the throttle it would start sputterin, is it possibly gettin to much gas?

[key4202003]

has ne1 tryed a 170 main with 40 piolt and a/f screw out 4 1/2 seems to work fine with my wb slip on and comments? also havnt took spark plug reading