How do i jet my carb?

[trx400exrider14]

I have a 2004 400ex and i want to get a performance series Hmf exhaust. I live at fairly low elevations. How do i jet my carb with the Hmf?

[dirtrider77]

HMF Recommended Jetting for 400EX (99-10)

1999-2009: Slip on: 165/170 Keihin Hex
1999-2009: Full System: 180/200 Keihin Hex

* These settings were determined on our dyno at 900ft - 60°F

[trx400exrider14]

yea but how do i do it to that settings?

[dirtrider77]

ohh gotcha, well lets act like theres not already 19759157 post telling you how to do this lol

1) remove carb
2) remove the bowl on bottom of carb by 4philips (be careful, they strip easy)
3)the brass hexagonal jet you see sticking up is the main jet...it will have a number on it
4)pilot jet will be recessed into a little hole and you will need a small flathead if you change it
5) buy an assortment of main jets around the HMF settings, start big and go down
6)adjust until it sounds good w/o crackling, popping, etc.

thats pretty simple and to the point if you want something more in depth just use the search feature

good luck!

[trx400exrider14]

i know there is,lol,but i just cant seem to find one that gives me that little piece im looking for.so if i get that hmf jet kit it will give me the new needle to put in? pilot and main?

[dirtrider77]

yes buy the $40 basic kit and it comes with 6mains and a 42 pilot...that will give you what you need

while you have the carb off go ahead and remove the choke by following this article:
http://www.atvriders.com/articles/choke400ex.html

and make sure you go ahead and put some type of aftermarket filter on (k&n, uni) while your at it to help increase the flow of things

that should spruce up the ole 400

---so personally if it were me....buy your pipe, and order the trail jet kit from HMF $70 ....comes with uni filter

..thats my advice for today

[trx400exrider14]

dude thanks alot! it helped me out

[dirtrider77]

anytime