2008-09 YZ450F User Jetting Database

24 replies to this topic
  • big bore morgan

Posted September 07, 2011 - 09:26 PM


hey guys im riding a 2007 yz450f....wanna know if i should have my crank blanced?? dont they come balnced?? its a hotrod crank..and im doing a 478 big bore,quick shot 2,slip -on.4.1// im riding in the cariboo so 3700 ft..what should i jet my bike too??

  • NewMexican

Posted October 20, 2011 - 04:53 PM


Model: 2008 YZ450F
Edit Revision Date: 07/14/11
Main Jet: 162
Pilot Jet: 45 (Stock)
Leak Jet (if any): 55 (Stock)
Fuel screw/Setting: 2 1/2
Needle/Position: NFPP-3
Filter: No-Toil
Pipe/muffler: FMF PowerCore
Altitude Range: 5500
Temp Range: 80 Degrees
Humidity Range: Low/Dry

Runs great, had stock 160 main on other bike (have two of the same model), major decel pop and raced at El Centro sea-level but it burned up crank (too lean). Rebuilt with big-bore and plan to run 165 main in it in the future, maybe go to JD red needle on it, but JD seemed too rich with stock cylinder.

Update: Bike above was rebuilt with the Cylinder Works +3mm big bore kit (478cc). I have renamed it my 505 (ala KTM), and since my NM area code is 505.

Anyhow, a lot of work has gone into these setting (tried 9 different set-ups, JD needles, 2 other YZ needles and a KTM needle as well, leaner and richer on pilot & main) and here is what I have settled on. Crisp, starts easier than my other stock YZ 450, pulls hard and all the way to the moon!

2008 YZ450F - Cylinder Works Big Bore kit, Hot Rods Crank, Vertex Piston

Main Jet: 175
Pilot Jet: 48
Leak Jet (if any): 55 (Stock)
Fuel screw/Setting: 2
Needle/Position: NFPR-3
Filter: No-Toil
Pipe/muffler: Stock/FMF PowerCore
Altitude Range: 5500
Temp Range: 80 Degrees
Humidity Range: Low/Dry

PS: It is now officially the hardest accelerating bike I've ridden since my 1989 CR 500!:thumbsup:

Edited by NewMexican, October 20, 2011 - 05:08 PM.
Add crank and piston and more bragging info...

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  • iveyyam450f

Posted November 12, 2011 - 12:47 PM


Model:08 Yz450F
Main Jet:185
Pilot Jet:65
Starter Jet:stock
Leak Jet:50
Fuel screw/Setting:2 out
Pipe/muffler: Jemco exhaust

*Comments: Carb has been bored and has a velocity stack from woody kyle racing and custom intake. Webb 963 cams.

  • lhf

Posted December 13, 2011 - 09:14 AM


Model: '09 YZ450
Edit Revision Date: 13-12-11
Main Jet: 165
Pilot Jet: 45
Starter Jet: Stock
Leak Jet: 55
Fuel screw/Setting: 2 turns out
Needle/Position: NFLQ-4th from top
Filter: TwinAir HiFlow Fire-resistant
Pipe/muffler: Akrapovic Full System
Altitude Range: 1000 ft. /300m
Temp Range: 50-90 degrees/ 15-30°C
Humidity Range:
Country: Germany

Comments: Needle with thinner Cylinder(***Q) stopps popping.

  • dadat40

Posted August 02, 2013 - 06:51 PM


Only change to carburetor I've made is 152 main to pro-longevity exhaust. I ride in Colorado 7600-13000 sometimes a bot rich above 10'000 feels good at lower stuff(7600-9000)

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