08 yz450f backfiring at low rpm, and on deceleration, looses idle... too lead..


5 replies to this topic
  • 29goat

Posted March 30, 2008 - 07:38 PM

#1

Looking for help, I just picked up a new 08 yz450f, started fine at the dealer with the choke on. Got it home, and it wouldn't hold a idle with the choke off. I turned up the idle screw which hepled. The bike will backfire with the throttle slightly cracked and will pop/backfire on deceleration. I think the carb is running lean, or is this how they run? other than this, the bike is great! any idea's? thanks

  • grayracer513

Posted March 30, 2008 - 07:49 PM

#2

Start by dumping the gas tank and adding some fresh. No telling how old the stuff in the tank is.

  • motox100

Posted March 30, 2008 - 08:14 PM

#3

I just picked one up Friday and it was a bit lean. Check you're fuel screw, I think mines about 2.5 turns out now

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  • 29goat

Posted March 31, 2008 - 08:22 AM

#4

Start by dumping the gas tank and adding some fresh. No telling how old the stuff in the tank is.

thanks, i'll give it a shot.

  • Ga426owner

Posted March 31, 2008 - 01:55 PM

#5

The fuel screw can be your best friend or enemy....get yourself a adj fuel screw. Temp and humidity affect this, as well as jetting that is not precise. After you dump old gas and use new, it is breakin time.....then rejet if necessary and adj fuel screw.

read this prior to breaking the bike in

http://www.mototuneu..._in_secrets.htm

  • racer 813

Posted March 31, 2008 - 02:16 PM

#6

Looking for help, I just picked up a new 08 yz450f, started fine at the dealer with the choke on. Got it home, and it wouldn't hold a idle with the choke off. I turned up the idle screw which hepled. The bike will backfire with the throttle slightly cracked and will pop/backfire on deceleration. I think the carb is running lean, or is this how they run? other than this, the bike is great! any idea's? thanks


This is dead on what mine did. I went up one size on the pilot to a 48 and one size on the main to a 165 and put the fuel screw at 11/2 and it runs great. I think this is pretty much what every body is doing around here.





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