Idle problems after rejet

6 replies to this topic
  • gpr

Posted December 20, 2008 - 04:53 PM


We put in a JD jet kit on my buddies 06 WR450f today and now we can't get it to idle right.

We put in the red needle with clip in the 4th position, 170 jet, AP mod.

Also removed the AIS, new K&N air filter and adjustable fuel screw (2 turns out). The exhaust is already uncorked, the grey wire is cut, the throttle stop shortened.

Once we got it started back up, it sounded a little rough but ran good while you stayed on the gas. Whenever you let off the gas, it dies out. Then it is difficult to get back started. We can't seem to figure out why it is not idling at all. Any ideas?

  • William1

Posted December 20, 2008 - 05:22 PM


Sounds like a vacuum leak. Double check the fitting the AIS drew vacuum from.

  • gpr

Posted December 20, 2008 - 05:30 PM


Which one would that be?

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  • ESYtiger

Posted December 20, 2008 - 08:47 PM


To embellish the above...

When we were installing a JD jet kit and was taking the top of the carb off, one of the plastic wheels fell off of the slide down in the carb and we had to take the slide out.

We also were doing the AP mod and somehow the spring lever by the throttle shaft got stuck back behind the wheel that holds the throttle cables.

We finally got the lever back into place and the throttle moves perfectly. The slide is also back in place.

The new needle and main jet are installed, but now the bike will not idle. When it hits it will run, but pull the clutch in and it dies.

What is the problem if the slide comes out?

Any ideas?

  • jhmotard

Posted December 21, 2008 - 11:00 AM


first make sure you put the slide in correctly....looking through the carb the hole should be on the bottom

secondly with more air going into the system via K&N you have to give it more fuel, which is the reason for poor idling. the pilot circuit is your idle circuit...bump up the pilot jet to a 48.

thirdly what is your altitude and temperature? i see your exhaust is uncorked but i think a 170 might be too much....if it was a slipon i might suggest a 168. try either a 165 or 168.

  • ESYtiger

Posted December 22, 2008 - 06:11 AM


The slide is in correctly and actuates smoothly.

The altitude here is 6-700 MSL.

  • jhmotard

Posted December 22, 2008 - 06:28 AM


if you have the snorkel removed too then...48p 165m 1.5 turns on the fuel screw


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