400ex with HMF is dieing under load. (HELP FAST)

[400exstud]

I just put my HMF pipe on when I am in neutral it revs out good but when I am in about 3rd or higher it boggs out and dies.

My jetting is a 180 main.
needle moved to the second from bottom
and mixture screw out 3 turns

PLEASE HELP ME, I am going on a week long trip tomarrow!

[sickmojave]

airbox lid on or off?

[400exstud]

lid is on + a quite core.

[sickmojave]

that sounds to rich to me..have you tried anything smaller than the 180?

[400exstud]

No, that is what HMF suggests but it really boogs out.
Will I be OK to ride it or do I have to go to a 175 NOW.


On my 5 min test of it the clutch cable broke!:(

[sickmojave]

you can ride it but it won't be much fun :( I would pick up a 170 and 175 and give them a try.

[400exstud]

I'll do that

Thanks a lot!

[400exstud]

I went to a 172 main and it still sputters a little but it is a ton better. I took the airbox lid off and it was perfet so tomorrow or tonight I will get a 168.

How does that sound?

I can't thank you enough sickmojave:D

[nosliw]

ive got a 155mj and my ex only has k&n (prefilter also), airbox lid on, no choke and no quiet core

[400exredrider]

180 sounds pretty rich...

[EvilJester400EX]

When I had my 400ex I had a 165 main jet in it with an HMF slip on.

[400exrider26]

what brand of jets are you guys running?

[nosliw]

keihin

[sickmojave]

Originally posted by nosliw
keihin


;) :D

[meanyellow03ex]

I've got a 170 kehein in mine with a HMF slip on and vented airbox lid. Was dyno'd to be perfect. With the airbox lid on, the 180 is too rich. either drop to a 165ish with the lid on or 170-175 with lid off. Good luck

[04'400ex'er]

you just looked at what they had on the inet didnt you? i called them and they reccomentded a 162 i think at 800ft thats with a filter and a full system. try a 165 that should be close to spot on

[sickmojave]

I just looked at their site and it said to use a 200 :eek2: :huh

[F-16Guy]

I don't care what type of exhaust you have, it's not going to require that you change the jetting from a 148 to a 180 (or even a 170 for that matter). I don't know who makes these jetting guides, but they're obviously not doing any R&D. You would need some SERIOUS mods to require a 180 main. I would suggest a 150-155, depending on temperature, altitude, etc. You are going to have to experiment a little. The right mixture is FAR more important than just cramming a bunch of fuel down your quad's throat.

[meanyellow03ex]

Originally posted by F-16Guy
I don't care what type of exhaust you have, it's not going to require that you change the jetting from a 148 to a 180 (or even a 170 for that matter). I don't know who makes these jetting guides, but they're obviously not doing any R&D. You would need some SERIOUS mods to require a 180 main. I would suggest a 150-155, depending on temperature, altitude, etc. You are going to have to experiment a little. The right mixture is FAR more important than just cramming a bunch of fuel down your quad's throat.

I'm running a 170 keihin. Thats with a slip on, filter, and a vented airbox lid. The quad was dyno tested and this was the optimum jetting to keep the air/fuel ratio between 13-14:1 . They put in a 155 to start with because everyone claims that the 155 is the best with those mods but it was running lean. Like 16-18:1 air/fuel ratio at 6000+ rpms. It put out about the same power as the 170, so driving it, you may have not noticed that it was too lean. Unless you dyno tune it, your guessing at jets with your assometer which isn't the most accurate way of tuning. But to say just put a 155 in, 170 is too big is not accurate. I live at 700 feet above sea level for comparison.

[MadMax27]

I have the HMF full, K180 main, with lid = waaay too rich. Dropped to K175, removed snorkel, still bogged on very top. K172, and turned the fuel screw in 1/2 turn did the trick for me. Runs like a raped ape now!! :D

[400exstud]

Just wondering but how hard is it to blow up a 400ex by rejetting for a pipe?

Well I made it through the week and my bike still runs. At a 168 main I could only go about 5 miles on a spark plug (full HMF + lid on and quiet core)

MY QUESTION IS: Does anyone run their bike with the needle at the stock position? Mine seems to be a bit rich.

[bonified5]

i have a hmf slip on and k&n and i run a 150 dynojet.