Anyone have jetting specs for the 08 yz450f???


7 replies to this topic
  • djtroy

Posted August 09, 2007 - 06:18 AM

#1

I was looking for a base to start twaking the jetting on the 08 450f. It backfires and seems to be a little lean and of course is not the easiest thing to start.
I am at 85-90 degrees at 600-800 ft elevation and 70-90% humidity.

South Carolina

  • Ga426owner

Posted August 09, 2007 - 10:56 AM

#2

Sounds like history is repeating itself....06...07 now the 08
go up 1 size on the pilot jet....and in this heat here in the SE 100degrees + with 80%humidity......good luck finding a good combo.....
adjust the fuel screw - I hope you bought a adj fuel screw....:thumbsup:

I had to go down 1 leaner on my mj on my 06 and up 1 richer on my pj...fuel screw adj in am will be different in the afternoon heat 1.5 - 2.5 range out

  • 07YZ450F

Posted August 09, 2007 - 11:22 PM

#3

wait... the bikes dont come with an adjustable fuel screw? or is the stock one not great? it would be kinda stupid to sell the bike without something it needs to perform properly wouldnt it?

  • Ga426owner

Posted August 10, 2007 - 05:24 AM

#4

wait... the bikes dont come with an adjustable fuel screw? or is the stock one not great? it would be kinda stupid to sell the bike without something it needs to perform properly wouldnt it?


the stock FCRs on all bikes come with a fuel screw that is recessed into the carb. It can be adjusted by a 1inch screw driver or by removing the carb...either way it is a real pain in the @$$, because there is no good way to tell how much adj is measured.
A adj Fuel screw is longer than the stock recessed screw. The decent ones have numbers on the end to measure exact turns in and out. All FCR equiped bikes need to have the fuel screw adjusted at some point to compensate for temp and humidity changes Richer/leaner conditions.
The Adjust Fuel screws cost about 20.00 and sure makes carb life/tuning easier. Unfortunately they do not come stock, but sure should. :worthy:

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • 07YZ450F

Posted August 11, 2007 - 05:01 AM

#5

yeah, i just found out how much of a pain that is this morning. i found something that works pretty decently until my fuel screw gets here (i ordered a Turner adj fuel screw), i took a 1/4" drive ratchet and put a 1/4" socket on it, took a flat head bit from a multitool i have slid it into the socket and used that. fortunetly it had lettering on one side so i didnt have to make any marks and i read it just fine.

  • Ga426owner

Posted August 11, 2007 - 05:35 AM

#6

I was looking for a base to start twaking the jetting on the 08 450f. It backfires and seems to be a little lean and of course is not the easiest thing to start.
I am at 85-90 degrees at 600-800 ft elevation and 70-90% humidity.

South Carolina


curious please tell me the stock jetting from the 08 manual....include the needle jet - NF.....part number, clip position mj , pj and lj

thx

  • Wes Woodin

Posted December 10, 2007 - 08:19 PM

#7

curious please tell me the stock jetting from the 08 manual....include the needle jet - NF.....part number, clip position mj , pj and lj

thx

Main jet #160
Pilot Jet #45
Needle Jet NFLR 5TA-14916-LR (Jet Needle Groove #3)
Leak Jet #55

Hope this helps

  • kristylynn9598

Posted December 11, 2007 - 05:12 AM

#8

This is what I have done. I am running stock pipe and silencer so you know.
And you know we ride at the same tracks just not the same speed there DJTROY.

I went up to 165 MJ (tried a 170 too but it got worse so went back to 165)
I went up to 48 PJ
I am between 1 1/2 to 1 3/4 out on fuel screw

Everything was running pretty good with a little hesitation with throttle just barely open. So I raised the needle one spot. It is now pretty good. Just not as crisp as it is 3/4 to full throttle. Next time I have it appart I am going to raise it one more see if it gets better or worse

It still has a pop to it but not a back fire like it did with the stock jets. With the stock jets it was actual fire and loud exposion type back firing. Now it just pops (Way different sound then before way softer and deeper with less of a cracking type sound) Hope that makes sense. From what I have read that should be normal.





Related Content

Forums
Photo

Is it worth it? (Cam and High compression piston) by macgi77


Dirt Bike   Make / Model Specific   Honda   CRF 150/230 F/L
  • Hot  36 replies
Forums
Photo

Snake pit oct 30th by The Anvil


Dirt Bike   Dirt Bike Regional Discussion   California
  • Hot  293 replies
Forums
Photo

YZ450F 03 Sparks driving me crazy by SirAttard


Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • 5 replies
Forums
Photo

Megabomb Fitment by 288yz450


Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • 1 reply
Forums
Photo

The "going back to the other darkside" adventure... by Monk


Dirt Bike   Make / Model Specific   KTM   250/350/450/505 SX-F & XC-F (4-Strokes)
  • Hot  94 replies
 
x

Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.