2007 yz450f jetting for high altitude

9 replies to this topic
  • ssyz450fss

Posted August 02, 2010 - 07:47 PM


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.

  • grayracer513

Posted August 02, 2010 - 08:17 PM


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

  • ssyz450fss

Posted August 03, 2010 - 06:17 PM


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.

  • grayracer513

Posted August 03, 2010 - 06:30 PM


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?

  • 2milehigh

Posted August 03, 2010 - 10:32 PM


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.

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  • grayracer513

Posted August 04, 2010 - 07:10 AM


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.

  • Wiz636

Posted August 04, 2010 - 07:41 AM


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.

  • ssyz450fss

Posted August 04, 2010 - 02:29 PM


Thanks, ill try evrything. I have and quickshot 3 adjustable leak jet.

  • pbviking

Posted August 04, 2010 - 03:01 PM


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

  • ssyz450fss

Posted August 04, 2010 - 03:17 PM


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

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