I have a 04CRF250X with CCC mods.
152 Main
40 Pilot
70 Leak
NCYS needle/4th groove
2 3/4 turns on air screw
I ride at about 1500' and seam to have lost some power in the cooler
temps (30d to 55d)
Any suggestions??

I would change the pilot jet to a 42, leak to a 55. Your main jet seems about right, as does your needle. If you change the pilot you will have to turn your air screw in some. I have a 150 main in mine and have ridden from sea level to 8K feet in temps from 25 to 85 and all i've needed to do was change the air screw.

N. Florida 150,42,5th clip pos, 2.25 turns a.s., somewhat opened air box, exhaust diffuser in but opened some at inward end.  The bike is still quiet but it rips now.  I can't believe how badly this thing ran before the mods.  I guess the EPA and california just want all these bikes to blow up from fuel starvation.

I have a 150 main, 42 pilot, raise needle on slot, fuel screw about 2 1/2 turns air box mod, and rick ramsey diffuser mod.  Im at 150' and its around 50-60 degrees.  I have had a huge improvement from stock but it still has a small bog when i wack the throttle.  It doesnt stall or anything but its not an instant rev.  Is this how it should be, or should it rev quicker?  How would perfect jetting in an X compare to a R in reving?  I was thinking about raising the needle one more slot, or just going to a 162 jet.  Any suggestions on jetting would be great.
Thanks,
John

Year: 2005
Elevation: 600 - 1000
Temperature Range:
Smog (AIS): No
Airbox Modified Top: Yes
Airbox Modified Sides: No
Backfire Screen: Removed
Air Filter: High-flow
Pilot Jet: 42
Main Jet: 150
Needle: Stock
Needle Clip Position: 4th
Fuel Screw Type: Zip-Ty
Fuel Screw Setting: 2 1/2 - 3
AP Modified: No
Leak Jet: Stock
AP Cover: N/A
Exhaust Type: Jardine Spark Arrested
Exhaust Modified: Yes
Pink Wire Modified: No

Kx65crazy said:

You've pretty much have the hot CRF250X jetting settings and shouldn't be experiencing " The Bog ".

*Edited*

I should have looked first for a better description on adjusting the Fuel-Screw before I posted. Linked below is an excellent ' how-to ' by AgentSmith I found over on the CRF450X Forum...

http://www.thumperta...925#post4340925

Hey guys I just went and purchased a bunch of new goodies for my '06 X.
I just picked up..
FMF power pack-header, tail section, and powernow
AP cover
twin flow air filter
airbox mod
and some jets the mechanic at the dealership (who owns an x with similar mods to me) suggested for me.

Anyways, after reading some other peoples posts the jets the mechanic suggested to me seem a little wack.

He said go with a 135 main, raise the needle 1 pos. from stock, 42 pilot, then turn mixture screw 1.5 turns out from stock.

Im  mainly worried about the main.  It seems way off of what people are usually using.

I ride in 60-85 degrees, 200-2000ft mainly. What do you guys think?  Thanks.

Hey guys, I ride anywhere from 4000'-6000'. I have a jd jetting kit, have done the air box mod, removed the filter screen, 160 main, ap o ring mod, and the red needle in the 4th clip. My leak and pilot jets are both stock, should i change those too?

2005 CRF 250X
JD jetting system
165 main
45 pilot
AB mod
TwinAir Power flow
AP o-ring
Red needle/ 5th position
Hotcam Stage 1
CRF fuel screw
Pink Wire
FMF Powercore TI
0-5000' elevation
No bog, no hesitation, no problem...

04 CRF 250X

250R Cam
Open Airbox
AP Mod
Baffle Removed
Pink Wire mod

152 main
42 pilot
NCYS needle
Fuel Screw 2 turns out

Runs Awsome!

2005 CRF250X
Yoshimura Slip On
All CCC Mods except cam (not yet anyway)
JD Jetting kit
-Red Needle 5th groove
-158 Main
-55 Leak

I ride Oregon trails between 1500' - 5000' altitude.  The Mods and JD kit definitely helped.  First and second gear power is great.  I am still dissapointed with the power in Third, fouth, and fifth gear.  Maybe I should have went with a CRF250R.  Does anyone know if the CRF250X with the Cam changed compare to a CRF250R? Thanks

I have a 05 250X...
R Cam.. 05 X Head.. Unported
Twin Air Filter
Back Fire Removed
Exhaust plug drilled out
JD Jetting Red Needle 3rd From Top
165 Main
42 Pilot
AP Mod, Wired together...
Wiseco Piston 13.5:1
Kibblewhite SS Valves, Intake and Exhaust
Now my leak jet is a stock 55.. I ordered a 70 thinking that is what I am suppost to go to.. but do I want the 55 or 70?? Or is it feel
I ride sea level to as high as I can ride, not sure how high
Most of the upgrades are new and I have not rode yet so I am sure it will be a lot of trial and error..
Am I close though?

Hey.  Just bought my 06 250x.  And, noticed "the bog" right away.  The guy at the dealer said I should come on here to get the specifics on jettin it right.  I've been doin ALOT of readin.  I'm in northern NE.  In New hampshire.  I ride in temps anywhere from 35-85 from spring to fall. An.... elevation is between 0 an 3000.  Don't wanna do the "pink wire" thing.  I bought an x, cuz I didn't want an "r".  But, was wondering the specifics on the airbox mod, anyone have a link or anything on how to do it?  An... what besides the jd jetting kit an the fuel screw should I do?  Something with the acc. pump?  do you guys think those three things would be enough?  I just wanna get rid of the bog, an get it runnin crisp.  Oh, an.. I'm putting a fmf Q4 spark arrestor slip on, on.  Don't know if tha t makes a difference in the mods that I need to do.  Any info would be awesome so I can get this thing runnin good quick, thanks!

Quote

Do the AP mod it will clean up the bog 100%

Heres a link.
http://www.motocross...rds_ap_mod.html

Heres some pick of my open airbox
http://s133.photobuc...=openairbox.jpg
http://s133.photobuc...openairbox2.jpg

SDK_CRFX_RIDER said:

Does it work the same as the "Quick Shot" aftermarket setup?

Just rejetted my 04 250x this weekend used a 42 pilot, 152 main, dropped the needle clip 2 notches and cut a hole in the top of the air box. Man what a difference like a whole diffrent bike. the thing pulls like a tractor and gets way better traction than my two strokes ever did.

My 2005 250/TMR 307cc X Jetting,165 main,45pilot jet,soldered up leak jet,accelarator pump arm wired to actuator arm,JD Blue needle standard clip position,all ccc mods,RHC 07 ported head,RHC 192 cam,FMF MegaBomb front pipe/Ti Q pipe, -4degrees of ignition advance runs great!

o4x 49 state,pink wire mod,open air box,defuser mod,42 pilot,158 main,ncys/ncyq needle,ap mod,wb fuel screw,55 leak jet,power now this thing rips (for a 250 4-stroke) fan kit next.....

04 250X

Mods
Airbox cut to CCC specs
AP Mod using strong o-ring
TwinAir Power-Flo Kit
Zip-Ty

JDJetting
165 Main
42 Pilot
Red needle 5th from top
1 3/4 turns on fuel screw

All else is stock.

:thumbsup: Wow! What a difference. Runs good all the way up to 7500'. Used very little choke when cold at 5200' 55deg, no hot start needed and no hesitation. Runs strongest from 300' - 3000'. :thumbsup:

Year: 2004
Elevation: 1,000 - 9,000 primarly 5k and above
Temperature Range: 50 - 100
Smog (AIS): No
Airbox Modified Top: Yes
Airbox Modified Sides: No
Backfire Screen: Yes
Air Filter: Stock
Pilot Jet: 42
Main Jet: 150
Needle: Red
Needle Clip Position: 4th
Fuel Screw Type: CRF's Only
Fuel Screw Setting: 1 1/2
AP Modified: No
Leak Jet: 55
AP Cover: No
Exhaust Type: Stock
Exhaust Modified: Drilled
Pink Wire Modified: Yes