Jetting problem?



6 replies to this topic
  • Ch35450

Posted June 04, 2015 - 05:47 PM

#1

Recently bought a '07 yz450f, in great shape, but I believe it is running a little lean...backfires and pops on deceleration and it idles up and down constantly when in neutral or when clutch is engaged. Has a fmf exhaust with the powerbomb I believe it's called? Correct me if I'm wrong.... and a hindle pipe, I'm wondering what I should run jetting wise? At about 300ft above sea level aswell as 0 to 30 degrees celsius, any help is appreciated thanks!

Edited by Ch35450, June 04, 2015 - 06:10 PM.


  • CRFRida1605

Posted June 04, 2015 - 05:49 PM

#2

Have you gone through the process of setting your idle properly, I found that will tell you if your pilot jet is right. You probably need to go one size up or maybe it just needs to be cleaned.

  • Ch35450

Posted June 04, 2015 - 06:09 PM

#3

Have you gone through the process of setting your idle properly, I found that will tell you if your pilot jet is right. You probably need to go one size up or maybe it just needs to be cleaned.


Yeah I messed around with it for a little and it still responds fine but even set at a lower idle it will still wander up and down by itself

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  • CRFRida1605

Posted June 04, 2015 - 06:12 PM

#4

How many turns out is the fuel screw?

  • Chuck.

Posted June 04, 2015 - 06:24 PM

#5

Wandering idle is a lean condition, likely caused by a dirty carb.  Also these bikes tended to be jetted lean which can also cause a hanging or erratic idle.



  • CRFRida1605

Posted June 04, 2015 - 06:26 PM

#6

Clean it then do this to be sure. http://www.thumperta...circuit-setting

  • grayracer513

Posted June 05, 2015 - 08:50 AM

#7

The wandering or "hanging" idle can also be caused by tight intake valves.  When they're too tight, they set up a lean condition by leaking combustion chamber pressure back into the intake tract and disrupting the airflow.







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