2009 yz450F jetting?

7 replies to this topic
  • bura76

Posted September 02, 2008 - 02:11 PM


Did you do anything with the jetting on the 2009 yz450f?

(my bike is compleatly original)

  • dirtbiker771

Posted September 02, 2008 - 02:47 PM


Just search jetting on the 08, the motor was unchanged in 09.

  • Emme

Posted September 02, 2008 - 03:59 PM


Had to richen it up. I went down one position with the clip. 170 main jet and a 48 pilot. That's in Wisconsin.

  • motoscotty

Posted September 02, 2008 - 08:02 PM


170 on the main ,stock needle 48 pilot.I had the AP worked on so I think they went down two sizes on the leak which is going richer.Zero bog and very very crisp.Moch improved over stock.

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  • Matt_W

Posted September 03, 2008 - 10:45 AM


I've been under the impression that the bog is caused by too much fuel. Back when I had my 2000 YZ426 the cure for the dreaded bog was to reduce the AP squirt. Back then I did the BK Mod and reduced the amount of fuel the AP was dumping in to the carb when you first whacked open the throttle.

Now I've been reading that everyone is making richer their pilot and main jets to eliminate the bog. I've only taken my 2008 YZ450F up and down the street a few times since buying it new, but notice there is some nasty hesitation when you wick the throttle hard. I've been reading about the O-Ring mod, although I don't think I have my head around why that is supposed to work.

  • DPW

Posted September 03, 2008 - 11:02 AM


my question would be are you having an issue with the stock jetting? My '08 jetting is all stock, no complaints.

  • jonkers

Posted September 03, 2008 - 09:36 PM


forget what jets i have n mine. Going to pull it out again soon so i will check it then.

I am running a NFLS needle. I also changed the leak jet but i can not tell you what to as i have an r&d bowl and it is adjustable.

  • motoscotty

Posted September 04, 2008 - 10:51 AM


my question would be are you having an issue with the stock jetting? My '08 jetting is all stock, no complaints.

I agree with you 100%,BUT with a little work it will run much much better..

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