2007 yz450f jetting for high altitude

I have been racking my brain trying to figure out the jetting on my 2007 yz450f. My altitued is 5800 ft. i have a new powerbomb header with a Q4 fmf and A power now valve. can some one give me some help.

Have you looked into the User Jetting DB in the index page?

Ya still had a bog so ilistened to a freind and it feels like im chasing my tail. Called fmf they gave me some pionters. but there is still a very little bog and the said get a aftermarket bowl. Know im woundering if the bowl is worth the money. the power now valve was supposed to clean it up. can i get some input on r & d power bowl.

The Power now will do nothing. The R&D bowl might help, but you can do exactly the same thing for half the money with a Merge Racing ALJ pump cover. The truth is that you can probably clean things up by timing the accelerator pump correctly (see the manual) and getting the jetting right.

What is your pilot/main combo right now?

Try these settings. When I ran these settings on my 08 the bike had an MRD exhaust and an R&D Powerbowl. Grey is correct about not needing the bowl, the same result can be achieved with just an adjustable leak jet pump cover. My 09 is running fine with the stock bowl and pump cover. If you go above 9500' for any long periods of time the pilot will need to be dropped one step.

5000' or higher

NFLR needle-2nd clip

48 pilot

158 main (160 main when temp is below 40*)

Air screw 2 turns out

5000' or lower

NFLR needle-3rd clip

48 pilot

160 main

Not promising these will work for you but I used and tested them for a season without any issues. Hope it helps.

IMO, the 48 pilot is too big.


Basing the jetting on 165/45 for a mean elevation of 2500 ft, and assuming 6000 ft for his, he should end up with something like 160 for a main, and either keep the 45 or go to a 42.

The YZ450 runs on the lean side just off idle to a 1/4 throttle. This may compensate itself due to the altitude, but it may not. In the latter case, you can try a needle with a smaller major diameter such as the NFLQ or NFLP. Part numbers are in the manual in section 7.

Last year I had a two day event up in Penticton, BC at roughly 6,000' and I went with a 42 pj and a 155 mj. In the mornings before the day warmed up I was running pretty lean and had to run my fuel screw way out but by the time the heat came I was pretty good and could fine tune with the fuel screw. The 155 main seemed fine.

At your elevation of 5,800' I would lean towards running a 155 main with the needle clip in the third position and a 42 pilot, especially with that silencer. Of course, this depends on the temperature and I would say that in the fall when the weather starts cooling down you would probably need to richen things back up a little.

i ride between 5500-10K

Here is how i did my 07 (that i can remember)

main is either a 158 or 160 I would guess its 160

needle is 1 leaner than stock

pilot is 1 richer than stock

air screw set at stock setting then adjust how the bike runs a turn out or in (usually a 1/4-1/2 fixes the problem)

runs like a charm

p.s. i running a dr d pipe

pilot is a 45 and main is 60 and 4th clip stock needle

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