CRF's Only Forums

Yep, just got off the CR500 and moving onto a 450X. I bought a new 08 and I've read about cutting the air box. I ride at 5000'-7500' elevation and from 40-95 degrees. Nevada is dry and open like SoCal.

So how about the Carb? (stock is FCR13B)
-Main jet size (stock is #145)
-Needle size (stock is NNEU) does this Needle from a 04' CRF450R work here also?
-Clip position (clip position fixed this year?)
-Slow/pilot jet (stock is#45)

Thanks for responding! I'll miss that oil burner

stock pilot is fine.
165 main jet
Yes the 04 450R needle will work great. For your elevation put in 3rd pos.
Part # NCVS 16233-MEN-671
I believe the 08 has a fixed Fuel Screw as well. So an aftermarket one will be needed. Look into the Crf's Only fuel screw. Its in the Catalog here online.

Welcome to the site.

thanks. what i have learned lately is...

-stock, sea level is good with no intake or exhaust mods. Maybe for break in period.
-Some think you can get away with the air box mod or removal of the exhaust baffle with the stock jetting, but not both.
-block off the smog equipment.
-a CRF450R cam.

?Do the JD kits come with smog equipment block off parts? I'm headed there (web site) next. How do you block off the smog equipment?

Rode for 2 hrs. on monday for the first time. I like this bike so far.

Airbox and Jetting is a must and needs to be done at the same time.

You have an 08, you baffle is not removeable like the 05-07's

JD kits come with 2 needles, a few main jets, and an o-ring for the ap mod, no smog block off stuff. Applied Racing makes a kit sold here. Or look in the stickies for smog block off done with JB Weld.

05 450R cam is a great mod. At that point Jetting will need Richened up a touch, and Pink Wire mod

Thanks

Spanish Springs?! That's near my old stomping grounds (grew up in Carson City, went to college in Reno). I still ride with my buddies in Carson (we recently rode at Sand Mountain) and my 2007 450X has ... as runs great with:

-Modified airbox including side slits cut out
-Aftermarket air filter with factory backfire screen removed
-stock idle/slow jet
-172 main jet
-NCYS needle on the fourth position (winter) and 3rd position (summer). Note: NCYS is a bit leaner than the NCVS. Done over I'd probably go for the NCVS.
-CRFs Only idle screw
-Pink wire mod
-Factory exhaust header with Pro Circuit T-4 slip-on muffler
-Aftermarket camshaft

Thus, if your bike is all stock (factory exhaust, cam, etc) with the exception of the airbox mods and aftermarket air filter, I'd suggest:

-stock idle/slow jet
-165 or 167 main jet
-CRFs Only idle screw (about 2 turns out)
-NCVS needle on the third clip position

If you later add aftermarket exhaust, up the main to a 170.

Scoot has pretty much nailed it with the exception of the fuel screw. It is adjustable but a pain in the a$$ to do it. There are a couple of different methods to make it easier. Some guys shove a wire butt connector over it to turn it. They also make a wrench which isn't worth the $40 they want for it. The other option is rotating the carb and removing the float bowl to adjust it. Here is what I have done so far and I have the same bike as you. I ride the same elevation and climate.

Year: 2008
Elevation: 4000+
Temperature Range: 40* - 100*
Smog (AIS): Applied Racing Block Off Kit
Airbox Modified Top: Yes
Airbox Modified Sides: No
Backfire Screen: Removed
Air Filter: Stock
Pilot Jet: 45
Main Jet: 170
Needle: NGGQ
Needle Clip Position: 4th
Fuel Screw Type: Stock
Fuel Screw Setting: 2 Turns Out
AP Modified: No
Leak Jet: 65
AP Cover: Stock
Exhaust Type: XR's Only Gen II Full System
Exhaust Modified:
Pink Wire Modified: Yes


I just got and adjustable Zipty Fuel screw that I should be installing here in a week or two. I need to dial my pilot a little bit, but so far the power and response is great from mid to top which kicks a$$ for open desert. I hope this helps.