2003-05 YZ450F User Jetting Database

23 replies to this topic
  • slothman

Posted December 14, 2012 - 04:23 PM


Model: 05 YZ450F
Main Jet: 165
Pilot Jet: 52
Starter Jet: stock
Leak Jet (if any):
Fuel screw/Setting:
Needle/Position: #5 from the top
Filter: Uni
Pipe/muffler: Bills exhaust header & pro billet muffler
Altitude Range: 200-2500
Temp Range: 40-70
Humidity Range:

  • smokingtz

Posted June 26, 2013 - 07:04 PM


[color=#282828][font=helvetica, arial, sans-serif][background=rgb(252, 252, 252)]Model: 03 YZ450F[/background][/font][/color]
[color=#282828][font=helvetica, arial, sans-serif][background=rgb(252, 252, 252)]Edit Revision Date: 6/26/13[/background][/font][/color]
[color=#282828][font=helvetica, arial, sans-serif][background=rgb(252, 252, 252)]Main Jet: stock[/background][/font][/color]
[color=#282828][font=helvetica, arial, sans-serif][background=rgb(252, 252, 252)]Pilot Jet: stock[/background][/font][/color]
[color=#282828][font=helvetica, arial, sans-serif][background=rgb(252, 252, 252)]Starter Jet: stock[/background][/font][/color]
[color=#282828][font=helvetica, arial, sans-serif][background=rgb(252, 252, 252)]Leak Jet (if any):[/background][/font][/color]
[color=#282828][font=helvetica, arial, sans-serif][background=rgb(252, 252, 252)]Fuel screw/Setting: stock[/background][/font][/color]
[color=#282828][font=helvetica, arial, sans-serif][background=rgb(252, 252, 252)]Needle/Position: unknown[/background][/font][/color]
[color=#282828][font=helvetica, arial, sans-serif][background=rgb(252, 252, 252)]Filter: stock foam[/background][/font][/color]
[color=#282828][font=helvetica, arial, sans-serif][background=rgb(252, 252, 252)]Pipe/muffler: stock[/background][/font][/color]
[color=#282828][font=helvetica, arial, sans-serif][background=rgb(252, 252, 252)]Altitude Range: 0[/background][/font][/color]
[color=#282828][font=helvetica, arial, sans-serif][background=rgb(252, 252, 252)]Temp Range: 40's to 90[/background][/font][/color]
[color=#282828][font=helvetica, arial, sans-serif][background=rgb(252, 252, 252)]Humidity Range: 0 to 100%[/background][/font][/color]

[color=#282828][font=helvetica, arial, sans-serif][background=rgb(252, 252, 252)]Comments: Ran perfectly since new. Never felt the need to mess with it. No popping. Starts fine. Runs stronger around 40 degrees. My 03 WR250F was another story.[/background][/font][/color]

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  • bluthndr

Posted September 19, 2013 - 05:10 AM


Model: 03 YZ450F
Edit Revision Date: 9/19/13
Main Jet: 175
Pilot Jet: 50
Starter Jet: 72
Leak Jet (if any):
Fuel screw/Setting: Moose(?) 2.5 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: Should be rich by the numbers, but actually runs great.  Finally tuned to where it will start good hot and cold, crisp throttle response, hot-start lever needed when hot (this is a first).  Unknown history of the bike means it may have cams and/or a big bore kit, but I don't know how to tell.  Seems to have more power than my friends' newer YZ450Fs (05, 06, 09)...

Edited by bluthndr, September 19, 2013 - 05:11 AM.

  • dattorob

Posted December 02, 2014 - 09:40 PM


Model: 05 YZ450F
Edit Revision Date: 03-12-2014
Main Jet: 168
Pilot Jet: 50
Starter Jet: 72
Leak Jet (if any): unsure (have powerbowl)
Fuel screw/Setting: 2 turns out
Needle/Position: NFLR , 2nd position
Filter: uni
Pipe/muffler: FMF Ti power core muffler, some custom ti midpipe and header
Altitude Range: 300ft
Temp Range: 60-100 F

Humidity Range: 25-50%

Comments: big bore kit (480cc), power bowl on carb, cams and porting (unknown), standard air-intake. Starting is not that great, hesitant/rough in mid throttle. 


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