2006 KX450f idle problems

Hey guys i have a 2006 kx450f and it has a strange idleing problem. I adjusted the idle and it sits at the proper idle. But when i hit the throttle a little bit even, it sits at a high idle. After i few snaps on the throttle it will go back down to regular idle then back up again if i hit the gas. Its a real big pain during riding especially because i will go to slow down but the idle being so high will make me go to fast into a corner and what not. I have taken apart the Carb and cleaned it out, just ordered a new throttle cable but after i put the carb back on i used a screw driver to turn the throttle on the carb due to me taking off the cables. Still doing it. Any ideas? Would much appreciate it.



Ok, so i did some research and i saw someone had the same problem as me and fixed it with the fuel/are screw. Well the guy i bought my bike off of had the screw all the way in. And i cant find what the stock setting is. Does anyone know? And he also put on a Powerbomb and Factory 4 exhaust system and i dont think he jetted it. So could my problem be, because of the jet or the mixture? I turned it out 2 1/2 turns. Do i need to do more? Please let me know. Im waiting for new throttle cables to come in this weds and doing a full fluid swap because the previous owner was one of the dumbest people i met in my entire life. Ex. Owned fir 2 yrs never once tightened the chain... Tyvm for the help.


06 stock jetting is pretty good. The 55 leak jet is usually better than the stock 70.

pilot = 42

screw 2.25 (+/- 1/4 turn depending on conditions).

needle = stock.

needle clip = middle or +1 (stock or richer).

main = 175 or 172 (stock or leaner).

If the previous owner had the screw in all the way, then perhaps the idle was set way high. That could mean it was lean and hanging high and/or the throttle position sensor never knows you want the throttle properly shut so the CDI wont reduce the spark advance. There is a chance the TPS is faulty, but sounds like you know the problem now.

Wont help a hanging idle, but next time the carb is off, check the action of your accel pump and condition of the AP diaphragm.

New throttle cables aint a bad idea. Check everything on the bike. Do more than a fluid swap. Consider reinstalling (locktite or lubing) most things like brakes, sprockets, bars, kick starter, hotstarter plunger and also re-grease the headstem, swingarm and linkage bearings. The spokes will probably need checking too, and maybe need some anti-seize on all nipple threads (remove rubber). If the piston age is unknown then just get it replaced with an after-market part. The stock wheels are pretty tough and light.

As you probably know, with good suspension and chassis setup it becomes a great bike and worth "restoring". The engine is beautiful and pulls tall gears with relative ease but still revs a long way. You'll probably like long start straights. After 06, the KX450 became 2 to 4 lbs heavier every year.

Yea man was thinking of doing most of what you said. That air/fuel screw was a hassle to play with cause the guy stripped it.... So i was tinkering with the bike from about 12pm to 3pm finally go it. Idle hangs still for only about 2sec so i don't really care to much about it. Before it wouldn't ever drop to idle. So im content and happy. I didn't want to move it and have it mess up again haha. Thanks a lot for you input btw!

Someone told me before to check the carb boots for an air leak. If air is getting in, it will create a lean condition, and a hanging idle.

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