lets have another fcr jetting thread!!!

[cals400ex]

well i have found a couple fairly long jetting threads for the fcr carbs. i have seen several people on here lately ask for jetting help with their new fcr carbs (including myself :D ). i am just wanting to be a little more specific than some of the other threads to help get these tuned in a little better. lets get started:

1. main fuel jet size
2. fuel skrew position
3. what needle
4. needle clip location
5. air skrew position
6. main air jet size

also, a brief overview of your motor mods, temperature its jetted best for, and your elevation if you know it. also, here are a few links to help tune your fcr and the other link is for the accelerator pump mod to eliminate the low to midrange bog. the normal accelerator pump will shoot fuel for somewhere between 4 and 6 seconds. this can cause the bog for our 400ex engines. i reduced time frame of the squirt to about .5 to 1.0 second. here are the threads:

http://www.exriders.com/vbb/showthread.php?threadid=49845

here is some fairly complex tuning guides for the fcr:

http://www.factorypro.com/tech/carbkei.html

[cals400ex]

i will start off to let everyone know where i am at right now:

162 main fuel
1.5 turns out on fuel skrew
i am not sure what needle yet
i am not sure what clip location on the needle yet
2 turns out on air skrew
200 main air jet


i also adjusted the accel pump so it squirts fuel for around 0.5 to 1.0 second.

i am running a 10.8:1 406, stage 2, x-6, uni filter, modded air box lid, and fcr 39 carb. it is 70 degrees and my elevation is 625 feet. the carb isn't dialed in 100% but the bike does run fine. after reducing the squirt of the accel pump, i do need to richen up the pilot jet for sure.

[moto93]

After doing the accel pump mod (thanks quadzilla) I found I was way lean too. Here's where I'm at now:

172 main
1.5 turns out on fuel screw
needle (stock) clip one down from center
air screw turned to where it idles best/fastest

Mods are:

11:1 Wiseco 440
Hotcam 2
ported head
Uni filter with no lid
Big Gun exhaust
39 fcr
procom cdi
15/36 gearing

It's running very good now but I'll keep tweaking!

Thanks for everyones help.

[cals400ex]

i think i will be tuning mine in with the accel pump not hooked up. i believe this is how your suppose to do it. alright, lets get more fcr owners in here. :D

[Chef]

What the heck is a main air jet?

[cals400ex]

Originally posted by Chef
What the heck is a main air jet?


the main air jet is located right next to the air skrew. you have to take the intake adaptor off and the main air jet and the air skrew are right there. it is basically another thing to tune in. :eek2:

if the bike runs good at WOT near the torque peak, but becomes lean towards the redline, you need a smaller main air jet. if the bike runs good near the torque peak but richens up near redline, you need a larger main air jet. this basically works with the main fuel jet. so, changing one may lead to a change in the other.

[cals400ex]

anyone else??