one more jetting question thread !

[Toxxin]

i opened up my carb for a cleaning today and i take a look at the jet and needle



i get a 2003 400ex with light mod that the previous owner did K&N power lid , K&N filter and the choke has been removed, stock evreything else



here what i found
170 main jet
38 pilot
4 clip from the top for the needle
and the fuel screw is about 2 1/2 turn out

sometime i get a bit of black smoke out of the exhaust i might be a lil rich ??

what do you think ?

[JOHNDOE83]

I would say its a lil rich, theres only one way to find out.

If you wanna try it yourself try this thread, I would say the needles the problem, put it in the middle and leave everything else unless you have problems in this thread, try a plug chop after the needle change?

http://www.exriders.com/vbb/showthread.php?s=&threadid=441780

[Toxxin]

i did read this thread and its confuse me more than anything else : /

[JOHNDOE83]

LOL...ya I can see how it can be confusing.

Steve, aka honda400ex2003, is great at trouble shooting and helping out in these situations, he'd be the man to help you out.

Right now, your biggest issue would be the needle setting, main jet might be slightly large but I like the main jet a lil big, if you dont sputter at wide open throttle Id leave the 170.

Deffinetly put the needle in the middle for now, I have a 440 big bore and still dont need to be on the 4th clip.

Im sure steve will chime in and guide you a lil easier then I can.

[Toxxin]

also if i ride steady at 1/2 throttle once in awhile the engine do a .. i dont know how to describe it but let say a hiccup , its not a back fire ethier

Lets hope honda400ex2003 chime in :) but for now i will try your tips and up the clip on the needle

[JOHNDOE83]

your pilot jet controls from idle to about 1/4 throttle, from 1/4 to 3/4 throttle is controled by the needle, 3/4 to full throttle is the main jet.

That would be the neddle being to rich giving you the hiccup at 1/2 throttle, does the jet you have with the 170 on it, have a flat tip screwdriver head to remove the jet?

if it does that would be a dyno jet kit, if its shaped like a nut "hex" but a lil longer, then its a regular keihin jet which is better then dyno jet.

[Toxxin]

its a 6mm hex jet the previous owner said its the jet that came with the K&N power lid kit

[honda400ex2003]

I would go with around a 155 main not a 170 make sure it is a keihin jet also. that is too rich for a stock machine. I would also suggest a 40 pilot to help with the starts when it is cold. keep the needle on the 3rd slot from the top which is with the needle part pointing down so it will stick in your foot if you drop it. lol. Ill post pics of dj style jets and keihin later if you are unsure. steve

[Toxxin]

well Rocky Mountain atv carry Pro X 99101-357 Series Keihin Hex jet is this ok ?? i have to order 2 new wheels this week from them... ill add some jet with it :)


what is the stock jetting of a 400ex ?

thx a lot for the help

Steve

[honda400ex2003]

I would say that they will work fine.

stock is 148 main,
38 pilot,
3rd needle position if you have the 04 and less(the new ones dont have adjustable needles)
2.25 turns out on the f/a

Glad to help. I would say that you should get from a 155 to 165 in case you decide to get an exhaust or something in the future. the 158 or 160 will be perfect with the filter, lid and a slip on. steve

[Toxxin]

great ! I will let you know how it turn when i get the new jet
thx again for the help

[honda400ex2003]

good luck! steve