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03 kx 125 carb swap

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So i have an 03 kx 125. Bike runs pretty good but has a notorious flat spot. It's got the stock mikuni tmx carb and word on the street (or this forum) is that they're junk. I have an extra pwk off a 05 kx 250 laying around that I was thinking about putting on to see if it would help out performance a bit. Has anyone ever swapped a pwk in one of these bikes?

Thanks in advance!

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The 05 250 carb won't work. It has the electronic stuff on it. We too have an 03 125 and an 05 250. The 125's is a Mikuni whereas the 250 has a Kehein. Yes, with enough ingenuity, you could make them work. But not worth it.

Your flat spot is due due jetting. Ours had the same issue. bad flat spot and sputtering. The best swap you could do is to give the 125 a 34mm carb. Otherwise, you need to lean it out and work with the needle clip position. I eneded up jetting the bike with a 370 main, 37.5 pilot and clip on top position. Even i pos. down on clip creates bad sputter. I was only one step away from ordering the leaner needle.

Also, what pipe do you have? It originally had a PC works pipe on it when we bought it. My son begged for the FMF and it made a night and day difference. The FMF rocked.

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hmm, i know the 05 carb has the tps and solenoid controlled powerjet, but none of those are needed and they shouldn't interfere with anything. I have a pc pipe and remember you posting about swapping to the fmf. This spot i have definitely seems like a lean one. I'll have to dig into it a bit more.

Sappers- Any interest in a wiseco pro lite for that 250 you just blew up? I a brand new extra one if you are interested. Pm me if you are

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