redrooster65 said:

This is what I run at higher alt

Year: 2004
Elevation: 8000-12000'
Temperature Range: 75 degrees F
Airbox Modified Top: Yes 4x4 or larger
Airbox Modified Sides: Yes left side has 2 sq in opening
Backfire Screen: removed
Air Filter: Stock
Filter oil: No Toil
Pilot Jet: 45
Main Jet: 155
Needle: stock
Needle Clip Position: 3rd
Fuel Screw Type: adjustable external
Fuel Screw Setting: 1 turn
AP Modified: Yes, thick o-ring
Leak Jet: Stock
AP Cover: Merge Racing ALJ
ALJ setting: 1 turn out
Exhaust Type: Stock
Exhaust Modified: Drilled baffle
Head Pipe: 2004-2005 R
Pink Wire Modified: disconnected
Cam: Hot Cam stage 1

When I'm in town at about 4500-6000' all i change is my fuel screw to about 2 turns out to shop popping on deceleration.

I have a 2007 CRF250X I bought used.  It has a FMF 4.1 complete system on it but everything else is stock.  It runs great and I'm scared to mess it up.  I don't see any recommendations for 2007 models and I know they had some carb changes that year.  If I cut open the air box does the 2007 model need a larger main jet?

04 250x

Decided to take a look at my wifes bike.  She barely made a few sandy hill climbs in a new area we have been exploring.  So I said well what the heck...

normal riding at 2000 to 9000 feet

airbox; stock
muffler; stock with insert in
needle; stock 2 grooves down from top
main; 130
pilot; 55
fuel screw; 2 turns out
slow; 68
leak; 65
Ap Mods; none, no orings

Decided to go with a JD Kit

airbox; opened the top per JD
muffler; stockw insert in (keep it quiet and we can all ride more)
needle; JD red at 4 grooves from the top
main; 155
pilot; 55
fuel screw; 2.5 turns out
slow; 68
leak; 65
Ap mods; thick oring!!

The bike way better but is still lean (boggs) a bit if you wack it wide open. I will going with a 55 or 50 leak jet to get more squirt into the motor.

Anyway, this worked great.  Easy to do.  and MORE POWER.

Peace,

Baja Joe

One little tid bit on the insert in the stock pipe...If you either drill a hole or cut off the defuser on the insert, you can gain some significant flow and power with out making the bike much louder...still very quiet and just a tad louder than stock...

How about jetting for 2006, 250x. 500-600 altitude. now in the 90's for temp.
FMF header, stock silencer.
snorkle off airbox.
currently stock jetting.
I wish I had enough power to get front tire up easier in 3rd gear.
I don't want to loss any torque.
I think prob
140 main
42 pilot.
Does JD kit come with all I need or do I still need to but jets.
Thanks,
Eddie

2007 CRF 250X
-Air Box Mod
-Twin Air Element (backfire screen removed/stock cage)
-Applied Racing smog pump removal kit
-FMF Powercore 4 Ti slip on (stock header)
-FMF Power-Up Jet Kit #012614 stage 2 (Specific for 07'-09' X models) not sure if this is a new kit?
-CJ134 Main Jet with supplied adapter(that is FMF's number)
-Needle on groove 5 from top (New needle included in jet kit, stock needle   only had one groove)
-2 turns out on the fuel screw

The FMF jet kit is a stage 2 kit specifically for 07'-09' 250X with removed snorkel on airbox, aftermarket filter and FMF exhaust as listed on instructions.  The bike has a noticible power increase and throttle response throughout the rpm range and sounds 10 times better!  Directions were spot on and very easy to install.

Very happy with results, no regrets.

Read quite a few posts and still don't know what's best.  I have the carb apart of my new to me 06 CRF250x.  I have yet to ride the bike (newly acquired project bike) but I would like to update the jetting of this completely stock bike.  This is my first post in the Honda forum coming from a WR450 and my first Honda!

What I discovered:
130 Main
40 PJ
55 LJ

I'm at sea level CA, the spark arrestor is missing (probably going to get a replacement) and I will be doing the airbox 4x4 mod.  Going to keep the bike stock otherwise.

Need to place an order here on TT soon any suggestions would be great.

Typical, never any info from 08 up:banghead: Did they improve the X that much in 08

Changing the Main to a 150 & the fuel screw in alittle made a big difference. Happy with that for now, & may do other mods down the road.
It isn't my KX 500 Mod, but it is a much better single track steed

2007 crf250x

800'-1200'
40-75 degrees
4x4 airbox mod
removed air filter screen
Twin air filter
pink wire mod
removed baffle
applied block off kit
Moose fuel screw 1-turn out (highest idle) and after that, I set idle screw til it purred
48 pilot
155 main
NCVT needle on the 3rd position from the top
stock leak jet
93 oct gas (Chevron always and only)
13/51 gearing (helped take away some of the bog and hesitation)
fuel line filter between tank and carb
Linkage is squirting straight into the head and missing the slide
AP mod doesn't need to be done on the 07 model
NGK Iridium alloy spark plug

It took me a little time and changing jets in and out, but I finally got my bike right where I want it.  Once I added the 48p, it completely took away all the bog and hesitation from idle to 1/4 throttle.  I can whack the throttle even on the stand and it DOES NOT hesitate at all!!!  Then when I opened up the airbox, removed the screen and baffle, I mean WOW, what a difference!!!  I added the bigger main jet at this point and the bike just rips from the very bottom to the rev limiter!!  Then the icing on the cake was getting the NCVT adjustable needle and once I got that dialed in, man, this thing is insane!!!!  I didn't know this bike had this kind of potential with a few free mods and $3 jets.  And a  my TT family was nice enough to give me the NCVT needle, 155 main and also, I traded my smog kit for a new block off kit!!  A guy in Cali from TT bought me a new block off kit for my smog unit!!!  This bike doesn't backfire, bog, sputter or hesitate at all anywhere in the throttle range.  Super crisp, snappy and will lug like a bear in the woods/hills.  The 13/51 was the cherry on top of the icing!!!  So much snappier than the 14/53, alot quicker acceleration, front wheel stands up so much easier and I can just lug it around with out clutch and stalling.  These bikes has so much potential with the right jetting, period!!

PS:  I will update the jetting in the spring and summer if it needs it.

Edited by GoonSquadRMZ450, 09 March 2012 - 09:58 AM.

Bajajoe, on 22 March 2010 - 04:08 PM, said:

The 55 pilot is way rich. Most end up with a 42 or a 45, some may end up with a 48.

Richer pilots and/or raising the needle (by lowering clip position) gets rid of the bog on these bikes. My riding buddies 2004 250x is running a 48 pilot,has no accel pump mods , and runs like a dream from single track to wide open fire roads.

Thanks for your input folks. I worked on the bike for 6 hours today after all the parts came in. I emailed JD and he answered twice within 24 hours. Being a novice mechanic and DIY'er I had more general questions for him and the install took me longer than I expected. I was curious why he recommended the 42 pilot jet on my bike when that is what it comes with stock. He told me that 45 and 48 pilots are used on "very unusual cases". Needless to say, I followed the directions to a tee and the horrible BOG is gone. Man, I was surprised after I took the bike for a test run. IT RIPS now compared to 2 days ago. The front wheel pulled of the ground in second gear and pulled all the way to 5th. I'm sorry for doubting a man that spends his days tunning carbs...

Anyway here are the final numbers and mods for my 2012 CRF250X California :

Location: Central California
Temp: 65-100F
Elevation: 48-4200'
Riding: trail and track
Mods:
Complete airbox mod
Air filter screen removed
Stock exhaust. Drilled 1/2" hole in end of exhaust diffuser, because the newer bikes' spark arrestor and baffle are welded to the end cap.
Applied Racing Emissions block kit, left equipment mounted just in case
Moose Aluminum Rear sprocket 53T stock size
Renthal counter shaft sprocket (front) 14T stock size
DID 520ERT2 Gold chain
Excel Black wheels and red hubs in stock sizes
Bridgestone 404/403 tires in stock sizes
Hardline tach/hour meter
JD Jet Kit(follow the directions, trust this man, he knows what he's talking about). Red Needle, clip in the 5th position from top, 42 pilot(which is stock size for 2012) 160 main(as per JD's direction with mesh air filter screen and airbox removed). Leak jet is 55 stock, so it was not changed. There is a special note that's easily missed in the directions regarding Keihin FCR carbs with "nail head" needle design and longer needle length(found on newer carbs). I missed these notes and panicked. The directions are complete.

What a huge difference. I look forward to riding this bike now and appreciate all the help.

Cheers.
Jay.