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klx 143 idle problems

5770 Views 7 Replies 5 Participants Last post by  Towlieee
I just installed a klx143 big bore kit, big valve head, and 26mm carbs

The bike runs great in all ranges, pulls hard right from idle to top end..

However the idle hangs if you blip the throttle, and drops slowly.. If i richen the mixture up, even a half turn, then I have to kick the idle screw way up to keep it idling..

Also when I cold start the motor, it idles very high for like 15 seconds or so, then comes down to a normal level..

I have the fuel screw turned 1.5 turns out. If I turn it out anymore, the idle doesn't go any higher, if I turn it in at all, it drops the idle drastically.

I'm lost right now as what to do.. The bike runs great just has a very erratic idle. I can't give it back to the owner like this, he's gonna think something is seriously wrong even though the bike runs great
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I built this motor for him, so he didn't have to pay the stealership $79/hr to build it...

Just trying to get it dialed in. I'm gonna wait tell tomorrow and go ahead and adjust the needle also and see if that makes any difference, I just got done riding it for about 20 minutes and I guess it does have a off idle hang where it could be smoothed out

I've tuned many carbs, from mini bikes to sport bikes, just never had a idle issue like this :confused:
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It has all brand new parts, new intake/carb/head/jug

I probably just need to play with it more, just the way the idle behaves has me lost.
Cokeham said:
sounds like my bike.. when you first start it, it will have a "racing idle", then goes down to normal after a couple seconds. the main thing that annoys me though, is it jumps when you click it into 1st, like if you dont have the brakes locked, youll be on your ass haha.. idk if that has something to do with the idle or whatever or if it's just a normal thing with big bores on these bikes w/o a clutch...

and like your bike, it runs perfect, so ive just let it slide... [after hours of playing with the carb!]

at least its not just me!

I ended up going up from 160 to 170 on the main jet (gonna order a 180 and see if that produces any more power), leaned out the needle 1 clip, and played with the idle more.. The idle is a little smoother, but still has a racing idle for the first 15-30 seconds, like it revs REALLY high. And the idle still fluctuates, sometimes it idles really low sounding like it'll die, then it starts to idle a little high, then just goes back down.. All while I don't touch the throttle, I just sit there letting it idle :(

But now it wont die, and the idle doesn't go too high or fluctuate too much, just goes extremely high on cold start.

I'm almost thinking maybe its the cheap knock off carb, or maybe its my tuning skills lol. I'm no expert, but I've never had a idle problem like this lol
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