Have an 06 klx250s with almost 5000 miles and my idle is set around 1300 rpms. At operating temperature when stopped at a lightor any other time my idle keeps changing, sometimes it will drop to around a 1000 and other times it will go up to 1700.Cannot figure out what is causing thisproblem, has anyone else experienced this?

Other than the idle problem the bike runs great with no problems.

Modifications are a HMF slip on, #40 pilot jet, #125 main, one shim under the needle and airscrew two turns out.

 

Just throwing stuff out...

Leak between carb & head.

Pin hole in or incorrectly installeddiaphram (you have carb apart then notice problem?).

 

Yeah, I would say the diaphram is a pretty good place to start. Usually, with an air leak between head and carb, you will get some pretty healthy backfires, but you didn't mention that was happening.

My vote is to double check if the diaphram is installed properly.

 

Yes, noticed the problem after taking the carb apart. It seemed at the time diaphram installed without issues, like it would only fit one way.

Thanks for the help, going to go through the process again this weekend.

 

Intake air leak somewhere between carb and cylinder would cause this...or like mentioned above...the diagphragm may not have sealed off in the carb causing the problem....It caused mine and i redid the whole schpiel and cleaned the mating surfaces and it was cured....live and learn right?...LOL....It had me stumped for a while till i thought about it.

 

Make sure you did not accidentally tear it or pinch it between the carb body & cover.

 

I had the same thing happen after I worked on the carb (one of the + dozen times I had carb off the bike) it was the diaphram not seated properly, which I suspected so I went straight in that direction.
I stuck it in a jar and let it soak in hot tap water for several minutes (to work out any kinks that it might have gotten from being assembled wrong) then it went right back together and ran fine.

 

I had the same problem and it turned out to be somthing really dumb. It was the throttle return cable. the one that pushes it back. The nut wasnt tightned all the way. HAha ...just a thought***

 

So far this is what I'll try: Check the rubber boot between the carb and intake, the diaphram in the carb, the return throttle cable and HMF told me to try turning the air screw out another 1/2 to 3/4 turn and perhaps my pilot jet is one size too small.

Everyones input is greatly appreciated!

 

I'd be amazed if your #40 "pilot jet is one size too small".