2003-05 YZ450F User Jetting Database


23 replies to this topic
  • MotoGoalie

Posted April 29, 2005 - 12:07 PM

#1

Since the bikes are somewhat mechanically similar here is a link to the WR guys; though we need you guys to put your info in too for the YZF ya know. :naughty:

http://www.thumperta...ad.php?t=230021

Model: 2003 YZ450f
Edit Revision:12/12/05
Timing:
Main Jet: 158
Pilot Jet:38 [COLOR=DarkRed](edited)[/COLOR]
Starter Jet: stock?
Leak: n/a
Fuel screw: Zyp Ty 1 1/2 turns out
Needle: #3 clip ( stock)
Air box: Twin Air and Unis
Pipe/muffler: Stock header, FMF Q (older version)
Altitude: 5700 feet and up to 11k
Temp:current 40-80F
Humidity: 30%

After Edit Satisfaction: Bike runs perfectly now. Lesson learned is that a very rich pilot and a very rich main jet seems to mimick a lean condition. High hanging idle, surging and sometimes hard to start. Except it could foul a plug.

Pre-edit, I'm on the verge of dropping the needle back down, ie placing the clip at the #4 position, back in the middle position to richen it up slightly.

#4 position at 8000 feet and 80'f was horrible, creating a rich bog in the middle and stumbling from 1/4 to 3/4 throttle. Probably because needle richness in conjunction with AP injection. #3 needle clip is best setting

I love the Q by the way. Its sufficiently quiet that you can now hear a lot of engine noise. Man these motors rattle and hum :naughty:

Degree of statifaction prior to the 38 pj change which was a 42: bike is g00d,no bog, good throttle response and runs like a striped ape WFO BUT it has a real annoying midrange surge that I cannot cure either with richer or leaner jetting, needle height etc. Sometimes hard to start.

Note: Temp has ranged from 70'f to 95'f recently so everyday its something different. Altitude has ranged from 5700 to 9000 feet.

As of 11-1-05 the current jetting is perfect for my conditions. Italics denote notes prior to finding a good combination of lean needle and pj range.

http://img.photobuck...Flagshroud3.jpg
clarke 2.8, XGX graphics, Utah skid, FMF Q

& my turkeybaster overflow
http://img.photobuck...verflowtank.jpg

  • yzhammer

Posted June 10, 2005 - 06:24 PM

#2

Model: 2003 YZ450f
Timing: YZ
Main Jet: 155
Pilot Jet:38 [COLOR=Red]Edited[/COLOR]
Starter Jet: stock
Leak:
Fuel screw: 1 1/2 turns out
Needle: stock at #3
Air box: no lid
Pipe/muffler: gyt-r aluminum
Altitude: 7000 feet and up
Temp:current 50-90 F
Humidity: 70%
Other:
Degree of satisfaction: Slight pop/sputter at steady 1/8 - 1/2 throttle still, but soooo much better than before I moved the needle. It is now very rideable, no surge. Tried a 150 and a 160 main, but the 155 feels the best. At full throttle there is no bog and strong power from beginning to end (of course, it's a yz450f).

Degree of satisfaction after edit: motogoalie had the answer. The 38 pj made this thing run absolutely perfectly. All sputter is gone, and it purrs like a kitten. I really am not exagerating. Perfect. :)

  • ncmountainman

Posted July 05, 2005 - 12:58 PM

#3

well i never would have thought it but;
2005 YZ450:

MJ: 160
PJ: 40
fuel:1 3/4-2 out
SJ: stock
LJ:40(stock)
needle: NDWR(04 wr450) 3rd clip (DWR needle is leaner than stock)
ALT:2k-5k
TEMP:70-90
HUM:60-70%
options; powerbomb header w/powercore 4-wide open,powernow,twin air screenless,boyesen quick shot. runs perfectly everywhere,starts great, no bog/stalling. only questionable thing is that when the hot start lever is pulled it doesn't idle up it starts to burble?

  • 35yz450F

Posted July 08, 2005 - 08:33 AM

#4

Model: 2004 YZ450F
Timing: YZ
Main Jet: 158
Pilot Jet: 38 :) [COLOR=Red](edited)[/COLOR]
Starter Jet: 70 [COLOR=Red](edited)[/COLOR]
Leak: N/A
Fuel screw: 1 1/4 to 1 3/4 turns out
Needle: stock at #3 position
Air box: unmodified w/Twin Air filter
Pipe/muffler: Powerbomb SX/Powercore 4
Altitude: 5700 to 7500 feet
Temp: 75-95 F
Humidity: 30% to 50%
Other: Dr. D +6oz. flywheel

Degree of satisfaction: I jet for the track at 5750 feet. I'm generally pleased with it like this. I've gone from a #40 pilot to a #38 and the bike runs even better now. I also went from the stock #72 starter jet to #70 and it starts even more easily. It looks like my settings are pretty much the same as Motogoalie's now even with the different pipes. I haven't been out on the trail at higher altitude yet, but it looks like we ride pretty much the same weather and altitude conditions.

  • 35yz450F

Posted November 04, 2005 - 09:15 AM

#5

The cold weather is here and I've fattened up my jetting for the cold air.

Timing: YZ
Main Jet: 160
Pilot Jet: 38 [COLOR=Red](edited from 40)[/COLOR]
Starter Jet: 70
Leak: N/A
Fuel screw: 1 1/4 to 2 1/2 turns out
Needle: stock at #3 position
Air box: unmodified w/Twin Air filter
Pipe/muffler: Powerbomb SX/Powercore 4
Altitude: 5700 to 6200 feet
Temp: 55-65 F
Humidity: 15% to 35%

I'm happier now with theses changes versus the mid summer specs with the cold weather. Just an occasional pop when chopping the throttle, generally happening when the track is just watered. The bike feels faster in the cold weather. I can't wait to ride a 450 at sea level.

Runs better with the 38 pilot jet at 65 degrees.


Summer specs:

Model: 2004 YZ450F
Timing: YZ
Main Jet: 158
Pilot Jet: 38 :banghead: [COLOR=Red](edited)[/COLOR]
Starter Jet: 70 [COLOR=Red](edited)[/COLOR]
Leak: N/A
Fuel screw: 1 1/4 to 1 3/4 turns out
Needle: stock at #3 position
Air box: unmodified w/Twin Air filter
Pipe/muffler: Powerbomb SX/Powercore 4
Altitude: 5700 to 7500 feet
Temp: 75-95 F
Humidity: 30% to 50%
Other: Dr. D +6oz. flywheel

Degree of satisfaction: I jet for the track at 5750 feet. I'm generally pleased with it like this. I've gone from a #40 pilot to a #38 and the bike runs even better now. I also went from the stock #72 starter jet to #70 and it starts even more easily. It looks like my settings are pretty much the same as Motogoalie's now even with the different pipes. I haven't been out on the trail at higher altitude yet, but it looks like we ride pretty much the same weather and altitude conditions.



  • Ga426owner

Posted December 13, 2005 - 01:54 PM

#6

2003 YZ450 with JD jetting kit at Ga weather and high humidity - Altitude 900 -2400 ft
Temps above 60 - F
Red JD needle 3rd or 4th clip
170main
stock pilot

Temps below 55 - F
Blue needle - 3rd clip
172-175main depending on temp
larger pilot

I do not ride below 45 -F period!

  • aford541

Posted December 17, 2005 - 10:34 PM

#7

Model: 2005 YZ450F
Timing: TPS and NSS disconnected
Main Jet: 170
Pilot Jet: 42
Starter Jet: OE
Leak:OE
Fuel screw: 1 1/2 to 2 turns out
Needle: stock at #3 position
Air box: Rear 1.5" trimmed off w/Twin Air filter or UNI
Pipe/muffler: WB Carbon Pro I
Altitude: 1100 to 2500 feet
Temp: 40-105 F
Humidity: 30% to 50%
Other: Head Ported, Carb done, power now front & rear u 4 fuel saftey wired accelerator pump

Degree of satisfaction: The bike is a superfast and I am pleased with it. like it is. I've gone from a #42 pilot to a #45 and back I think the U4 clogged up my pilot jet.

  • MotoGoalie

Posted March 21, 2006 - 07:46 AM

#8

Model: 2003 YZ450f
Edit Revision:12/12/05
Timing:
Main Jet: 158
Pilot Jet:38 [COLOR=DarkRed](edited)[/COLOR]
Starter Jet: stock?
Leak: n/a
Fuel screw: Zyp Ty 1 1/2 turns out
Needle: #3 clip ( stock)
Air box: Twin Air and Unis
Pipe/muffler: Stock header, FMF Q (older version)
Altitude: 5700 feet and up to 11k
Temp:current 40-80F
Humidity: 30%



Cut and paste this template for your bikes setup.

  • chrisn6104

Posted April 26, 2006 - 12:44 PM

#9

Model: 2003 YZ450f
Timing:
Main Jet: 164
Pilot Jet:42
Starter Jet: stock
Leak: stock
Fuel screw: Stock 2 turns out
Needle: #4 clip stock needle
Air box: No-Toil filter and oil
Pipe/muffler: Dr.D SS with arrestor
Altitude: 4000ft-5000ft
Temp:current 80F
Humidity: dry

Bike is very strong no hesitation but very hard to start. Takes 4-5 kicks to start after it's warm. Pops on decell.
Any suggestions? I was thinking about just trying next size down pilot. WIll that help with my starting?

  • chrisn6104

Posted July 21, 2006 - 11:09 AM

#10

Model: 2003 YZ450f
Timing:
Main Jet: 162
Pilot Jet:40
Starter Jet: stock
Leak: stock
Fuel screw: Stock 1.5 turns out
Needle: #4 clip stock needle
Air box: No-Toil filter and oil
Pipe/muffler: Dr.D SS with arrestor
Altitude: 4000ft-5000ft
Temp:current 90F
Humidity: dry

The 40 PJ seems to be about right. 38 was to lean 42 is hard to start. I went out for a weekend about 1500ft higher then where I live. Bike seemed to run slightly rich on the trails but still easy to start. However I think I can go bigger on the main (at least up to 164) I'm going to see how big is to big.
Starts within 5 kicks when cold and 1 kick there after. Only a slight pop on decell after a few seconds. I guess thats to be expected with the aftermarket exhaust.

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  • BC3

Posted April 19, 2007 - 12:13 PM

#11

Just drug the 03 450 out and dusted it off....I started it up and rode down the
street and she still scares me....I have a 45 pilot and 165 main. Fuel screw is 2 turns out. needle stock position, and a E-Series pipe with 12 plates ...Runs perfect, idles, no poping....

  • Benzie

Posted July 16, 2007 - 05:03 PM

#12

Bike: 05 YZ450
Main Jet: 162
Pilot Jet: 48
Starter Jet: stock
Needle: Stock
Leak: stock
Air box: Stock/ Twin Air
Pipe/muffler: Yoshimura TRC Pro Series
Altitude: 0 to 1000
Temp: Mid 60's to 80's

  • shortburb

Posted July 27, 2007 - 04:05 PM

#13

03 yz450f current specs
Main Jet: 162
Pilot Jet: 42
Starter Jet: 72
Fuel Screw: 1-1.75 turns out
Leak: ?
Air box: stock box K&N filter
Pipe/muffler: big gun full no sparky
Altitude: denver 4800-5800?
Temp: summer 80-100f

as it sits it runs decent in town no real bogs/misses. 1 kick cold, sometimes 8+ hot(even with hot start) HORRENDUS popping on decel.
in the hills it has a noticble low rpm bog (thought it was fouling a plug at first....bog bog-rrrrriiiiiiiiiiiippppppppp ) but runs fair up high. still super bad popping.

gonna go 38 pj and 160 mj 70sj (motogoalie is skaking his head at me i bet for 3 changes at once) and retest.....

  • calilsv

Posted January 22, 2008 - 01:54 PM

#14

Bike: 05 YZ450
Main Jet: 165
Pilot Jet: 48
Starter Jet: stock
Needle: Stock
Leak: stock
Air box: uni filter
fuel screw 1 1/2
zip ty carb mod
Pipe/muffler: GYTR stepped
Altitude: 0 - 2000
Temp: 40s to 50s

Runs good, has not bog, and plenty of power. I'll probably switch back to a 45 Pilot in the summer.

  • grayracer513

Posted September 22, 2008 - 08:04 PM

#15

READ BEFORE POSTING!: This thread is intended to be used as a reference collection of jetting used by members ONLY. Please use the provided template below, and post only the jetting you currently use, along with any pertinent comments. Post only in the correct thread for your model bike.

DO NOT ask questions or discuss the information posted here in this forum. If you want to talk about anything here, please do so in a new or current thread on the topic and use a link to the particular post you wish to discuss. Posts not complying with this format will be removed without comment.

NOTICE:The people who post here are of all skill levels. This information is only intended to let you see what others are using, and cannot be taken to mean that the information is accurate, will apply to your use correctly, or even that the poster's bike runs right with the posted setup. Use it as a guide/starting point only, and look at as many relevant postings as you can before proceeding.

POST ONLY INFORMATION APPLICABLE TO 2003-05 YZ450F MODELS IN THIS THREAD.

Post your jetting using the template below (copy and paste to your post) and please be as complete as you can. In the Comments section please include any modifications you feel will have a bearing on the jetting, such as cams, accelerator pump mods, bored carbs, etc.

*************

Model:
Edit Revision Date:
Main Jet:
Pilot Jet:
Starter Jet:
Leak Jet (if any):
Fuel screw/Setting:
Needle/Position:
Filter:
Pipe/muffler:
Altitude Range:
Temp Range:
Humidity Range:

Comments:

*************

OEM 2003 YZ450F® Jetting:

Main Jet: 165
Pilot Jet: 42
Starter Jet: 72
Leak Jet (if any): N/A
Fuel screw/Setting: 2.0-2.5 turns out
Needle/Position: NCVQ-4

OEM 2004 YZ450F(S) Jetting:

Main Jet: 165
Pilot Jet: 42
Starter Jet: 72
Leak Jet (if any): N/A
Fuel screw/Setting: 2.0-2.5 turns out
Needle/Position: NCVQ-4

OEM 2005 YZ450F(T) Jetting:

Main Jet: 165
Pilot Jet: 45
Starter Jet: 72
Leak Jet (if any): 40
Fuel screw/Setting: 1.75-2.25 turns out
Needle/Position: NFLR-4

  • Benzie

Posted November 04, 2008 - 09:35 AM

#16

Model: 05 450F
Edit Revision Date: -
Main Jet: 165
Pilot Jet: 48
Starter Jet: Stock
Leak Jet (if any): Stock
Fuel screw/Setting: 1.5 Turn out
Needle/Position:#3
Filter: Stock/Twin Air
Pipe/muffler: Yoshimura TRC Pro Series Carbon Fiber w/ muffler shortened 3"
Altitude Range: 500' above
Temp Range: 50-80
Humidity Range: 30-80%

Comments:

Bike is ported/polished with rev box.

If i throw on stock exhaust i run a 162-3 main jet, when its colder than 50 i bump up the main to 168.

Has slight hesitation from idle to quarter throttle, but runs great otherwise.

  • tek_01

Posted January 16, 2010 - 11:00 PM

#17

Model: YZ 450F 2005
Edit Revision Date: 17/1/10
Main Jet: 165 (stock)
Pilot Jet: 45 (stock)
Starter Jet: stock
Leak Jet (if any): stock
Fuel screw/Setting: 2 turns out
Needle/Position:stock
Filter: twin air
Pipe/muffler: Jardine RT-4 full system
Altitude Range: Sea Level
Temp Range: 10 - 40 deg celcius
Humidity Range: 50 - 80%?

Comments:
Bike runs really well, no bog and very very little popping on deceleration. Will start 2nd kick cold (no choke on most day) with 2 turns of the throttle.
Hot it will start first kick with hot start lever pulled unless it is in gear than it may take 4-5 kicks.
I have the merge Stiff AP spring and adjusted the AP squirt to just miss the slide, Has no perceivable bog at all.
Did not need to change jetting even with new exhaust although i have a large pilot on order

  • nesc522

Posted August 21, 2010 - 04:25 AM

#18

Model: YZ 450F 2003
Main Jet: 170
Pilot Jet: 52
Starter Jet: stock
Leak Jet (if any): stock
Fuel screw/Setting: 1 1/2 turns out
Needle/Position:middle
Filter: stock
Pipe/muffler: Yoshimura Full exhuast
Altitude Range: Sea Level
Temp Range: 70-80 degrees
Bike starts easily, hot or cold, tried jetting with specs already posted here and with a 42 pilot, jetting was very lean and starting was difficult.

  • homernukem

Posted February 06, 2012 - 03:38 AM

#19

[color=#282828]Model: 05 YZ450[/color]
[color=#282828]Edit Revision Date: 2-6-2012[/color]
[color=#282828]Main Jet: Stock 165[/color]
[color=#282828]Pilot Jet: 150[/color]
[color=#282828]Starter Jet: stock[/color]
[color=#282828]Leak Jet (if any):stock[/color]
[color=#282828]Fuel screw/Setting: 2 turns out[/color]
[color=#282828]Needle/Position: stock[/color]
[color=#282828]Filter: UNI[/color]
[color=#282828]Pipe/muffler: Stock[/color]
[color=#282828]Altitude Range: 2400 feet[/color]
[color=#282828]Temp Range: 65 degrees [/color]
[color=#282828]Humidity Range: probably 40%[/color]
[color=#282828]It idled like crap and was poping like crazy with the 45 pilot i installed the 50 and it is a freekin dream. I love it. I may mess with the other jets soon.[/color]

Edited by homernukem, February 06, 2012 - 03:40 AM.


  • bluthndr

Posted June 11, 2012 - 04:29 AM

#20

Model: 03 YZ450F
Edit Revision Date: 6/11/12
Main Jet: 170 (was 175)
Pilot Jet: 45 (was 50)
Starter Jet: 72 (stock?)
Leak Jet (if any):
Fuel screw/Setting: Moose(?) 2 turns out
Needle/Position: unknown
Filter: stock foam
Pipe/muffler: C4M full exhaust with header
Altitude Range: 600'
Temp Range: 60- 80's
Humidity Range:

Comments: Actually ran really good with the richer 175 and 50 jets, but starts significantly better with the 170/45 setup. Did not "pop" with the fatter jets on decel, but does now. Power and response of both setups is similar the only differences I noticed were the popping and easier starting with the leaner jets. Still tuning the bike. More to come...





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