Jetting a 400ex

[Sleeper]

Originally posted by roostonu
My stock needle on my 400ex dosent seem to be adjustable but Ive seen Dyno Jet needles with the grooves in them.Is there any adj. on the stock one or do you have to use the D.J. needle?

Your stock needle is adjustable. Have you removed it?

Sleeper

[Sleeper]

Originally posted by Honda6sv
I have UNI air filter (with open aluminum air box) with FMF high flow header and powercore 4 slip on...How should i go about jetting the carb..What would be the best to use?...everything is stock except air filter and exhaust.

I got the parts from my local honda dealer. They buy the jets in bulk from the carb manufacturer. There's only 2 parts you need to buy (the pilot jet & an assortment of main jets). The rest is adjustable. what jets you will need depends on your altitude where you ride.
I have a similar set up except I have a cam. I ended up with a 42 pilot jet, a 162 main jet, I moved the needle clip 1 notch down and I turned out the mixture screw until it pretty much stopped popping out the exaust when I let off the throttle in gear and left the clutch engaged so the engine was slowing me. I think I'm an extra 1/2 to 3/4 turns out.

I am a little just a hair lean over all at around 850 ft but I ride most around 2000 ft elevation so I will be rechecking latter. Should be good though.

This is just a refferrance.

Edit: I am up to 168 on the main now and I think it's pretty close.
I finally got somewhere I could really wind it out and kill it (like your supposed to).

Sleeper

[Honda6sv]

Well, I live it iowa
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and my stock jet is a 148, and pilot was a 38...I bumped the pilot to a 40, moved the needle down one notch, and left the main jet...Im thinking bout trying one or two sizes on the main as well...thoughts?????

[DAVE14]

Ive been meaning to adjust my needle jet but havent gotten around to it it runs well & plug looks great but stumbles sometimes on its way up to high revs when you give it to her all at once I have a 42 pilot & 170 main (440) 350 foot elevation I havent seen it from the bottom where is it & can I access it easily ? pics would be great thanks

[EricCartman]

I just thought I'd post my settings to help out anyone with my set-up.

2004 Honda 400ex - K&N filter, modified lid, stock exhaust with tip opened up, Sparks timing advance.

My carb: 155 Main, 42 Pilot, shim washer under the 3rd clip position of the needle.

Runs great! A lot more power than stock. Plug shows it's close to being tuned correctly. At or near sea level.

[blacklabel117]

yah iv got a 400ex 05 and i just ordered a k&n air filter and it has a white brothers slip on and then i ordered a 150 and 152 main jet just to c wat one was better then i got a 40 pilot jet will those work???? and what shuld i do with the needle?

[Rip_Tear]

Just leave the needle alone. If it was already jetted for the white brothers pipe you might not need to rejet. If it wasn't jetted already, I'd suggest going with the 152 to start with. Go for a quick ride, check the plug (you should get a new plug for testing purposes). If it's a nice brown color (like carboard) you are good, if it's darker (black) then move down to the 150 and test again. The needle is for fine tuning so if the plug is close but not quite right, move the needle (up for more gas, down for less). If the plug goes white (harder to tell with a new plug but the tip will usually go white) you need bigger jets. For your mods those jets should be fine.

Hope this helps, haven't done this for some time, so I hope I haven't mislead you.

[blacklabel117]

hey thanks man i will try it all out when i get my parts in thanks again i will let uk how it went

[blacklabel117]

ok guys so i put the 40 pilot in and left the 148 main in otherwise if i put the 150 or 152 in it was rly stumbly and crappy but the 148 is working with the 40 nd to b honest its kinda stumbly but good is that normal?

[Rip_Tear]

So maybe you just need a 149 if it's better with the 148 then the 150 or 152. You could raise the needle all they way up or one notch at a time and see if it helps. (when I say raise the needle I do mean so that the needle sits higher allowing more gas to flow).

What color plug did you get? I know it's annoying to check the plug color but some times you have to. Also was it running good before you did all this to it?

Remember, white is bad, brown is good, and black is bad but better then white, for plug color. An old plug won't give you a proper reading, and even though the motor runs fine it doesn't mean it is jetted correctly.