2006 KX250f-FCR

[D1PP1N]

Ok here are my issues.

I have all stock jetting and from bolingbrook illinois- I believe is about 300-900 above sealevel. I have an MSR fuel screw also. Its set to about 2.25 turns out. The bike is also stock except for a twinair filter and new clutch/springs

1. When I start the bike its idles fine. When I hit the throttle after its warmed up for abit and get ready to head out when I close the throttle (let off of throttle) it idles alot higher then it should (inbetween 4k-5k rpm) for a few seconds (1-12 seconds) and then settles at the regular idle speed (2k + or - 50 rpm). It does it when I riding or warming up. Kinda scary cuz it pulls me into turns when I dont want it to and i overshoot them. Then others it goes down to idle and I slow down way b4 im supposed to.

2. At first i thought the throttle was set wrong. So i loosened the accellerate and decellerator cables and then back off the decel all the way (it actually unthreaded so i screwed it back on a few threads and stopped) then I set the freeplay with the accelerator. Hopefully there isnt anything wrong with that.

3. I have purchased a #42 pilot and the stock one I believe is a #40. I messed with the fuel screw abit but didnt see a huge change. It Just lowered or made idle higher but didnt cure the problem.

4. I would start changing the jets but im afraid I will mess something up. I only get to ride maybe 1 time a week so my riding time is very valuable to me I really dont want to spend the entire day jetting. It runs fine everywhere else and I am kinda just getting used to what its doing. But i would rather have it fixed.

Thx in advance for the help.

[VAHSMXRIDER]

When the it idles high and then goes back down to normal this means the mixture is a little lean. Try turning the fuel screw out a few 1/4 turns. I had the same problem with mine. It is pretty scary to overshoot the turns.

[D1PP1N]

so go to I have it set to soemwhere around1.75-2.25 so go to 2.50 or 2.75 then?

[AlloyMx95]

Sounds too lean to me. You really need that 42 pilot. Just put it in as soon as you get it then set the fuel screw every day before you ride.

[Wayward Son]

https://www.thumpertalk.com/forum/showthread.php?t=327405

[D1PP1N]

Im just trying to understand the what exactly the fuel screw does. Like what am i looking for when its set to its optimal spot. I have read the article and followed it when i tried to set the fuel screw last ride but I dont understand what you mean by it peaks-. Like with a 2-stroke it was easy, turn the air screw until the throttle response was crisp and your done. Now that I have to turn the fuel screw and idle screw. When im dealing with the fuel screw what should the idle screw be at? Just get it around 2k rpm? Cuz if i hit the throttle at all it jumps to 4-5k rpm and im back at square one again. Im just getting frustrated with it now.

[AlloyMx95]

Unless it is above 85 degrees at the altitude you are riding at you need a 42 pilot jet. I would do that first. If it is below 45 degrees you need a 45 pilot.

[D1PP1N]

Ok, I wont be riding saturday so i have the entire day to get it fixed then. I'll get it powerwashed and pull the carb tommorrow b4 work. Thx again Alloy.

[D1PP1N]

OK I DID EVERYTHING YOU GUYs said, went to a 42 pilot accelerates alittle better but thats its. I set the fuel screw/idlescrew and I still keeps fueling when the throttle is closed. I made sure the play was correct with the side cover off. So it must be the AP or leak jet? Whats next?

[barton]

Hanging idle is lean. You're getting extra air somewhere. Check your intake tract for leaks. Squirt starting fluid (carefully, it's very flammable) at all the joints in the intake tract while it's idling. If the idle speeds up you've found the leak.

If that doesn't do it, make sure your hot start isn't stuck open. Remove the hot start cap and plunger from the carb, and inspect the o-ring. Replace it if it's torn, and put a very small amount of grease on it, and re-install.

[D1PP1N]

I just had everything off and taken apart, the hot starter plunger is fine and I put alot of slack on it now. Im sure that the air boot is on correct also I had the subframe and rear shock off. I'll do that and check for leaks perhaps i have a rip somewhere.

[AlloyMx95]

OK I DID EVERYTHING YOU GUYs said, went to a 42 pilot accelerates alittle better but thats its. I set the fuel screw/idlescrew and I still keeps fueling when the throttle is closed. I made sure the play was correct with the side cover off. So it must be the AP or leak jet? Whats next?

Does it still have a hanging Idle?

[D1PP1N]

Yes, It still has a hanging idle. I tried the starter fluid thing also, but idle didnt change a bit. I checked the fuel screw to make sure all the oring was in there and it is. Whats next down the line? with the .42 pilot its boggy of the bottom now also. I think its alittle too rich.

[D1PP1N]

Anyone ^^^

[James_Dean]

Look for pinched cables, cable freeplay, air leaks , check the float level, and lastly remove the carb and inspect the slide to see that the slide plate is in good condition and that the slide has the square end downwards.

See-

James