2003-05 YZ450F User Jetting Database

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:

Model: 03 YZ450F

Edit Revision Date: 6/26/13

Main Jet: stock

Pilot Jet: stock

Starter Jet: stock

Leak Jet (if any):

Fuel screw/Setting: stock

Needle/Position: unknown

Filter: stock foam

Pipe/muffler: stock

Altitude Range: 0

Temp Range: 40's to 90

Humidity Range: 0 to 100%

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.

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

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. 

:aussy:

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