[jsnotech]

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

[Skoot22]

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.

[jsnotech]

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.

[Skoot22]

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

[jsnotech]

Thanks

[Kiwi]

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.

[belltownjefe]

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.