200 EXC poppy/stutter at mid throttle.

A buddy of mine has a 2004 200 EXC and when trying to smoothly roll on the throttle, somewhere in the low-mid to mid throttle range there is a poppy stutter that just kind of feels like the ignition is cutting out or the fueling isn't right. The reeds have just been replaced and carb cleaned. The problem has been there since he bought the bike a few months ago. It has a new plug. Could it be a gummed up powervalve? He hasn't had that apart. Im pretty unfamiliar with KTM. I know a good amount about two strokes but this has me a little baffled. I would appreciated any and all advice/suggestions.

Sounds like jetting. I have spent many hours on this forum and on ktmtalk dot com sorting out this very thing. The Good news is that it can be fixed. I got in pretty good shape with a JD red needle. And have heard good things about using Sudco needles, which is my next thing to try.

I would suggest posting up all your jetting specs so the pros around here can look them over. Include temps, elevation, gas/oil ratio, oil brand, pilot jet, main jet, needle, clip setting, slide size, etc.

Thanks. We will tear it apart and have a look at the specs.

You say you cleaned the carb. If you dipped the carb in carb cleaner then you may have ruined the jet block o-ring. This part doesn't show up on the Keihin parts diagram. The jetblock is the small assembly bolted to the bottom of the carb assembly that the jets bolt into. If you look close, there are 2 tamperproof bolts that hold this assembly in place. There is a small o-ring between the carb assembly and the jetblock. If you dip the carb in carb cleaner, this can get ruined and mess up the jetting. You can find these o-rings online for ~$10, just google jetblock o-ring. Keihin doesn't list this one particular o-ring because they'd rather sell a complete carb housing when people can't figure out what's wrong with their carb.

We cleaned the carb by disassembling it and spraying the individual parts clean with carb cleaner. I guess I've never heard of just dipping the whole carb in cleaner, doesn't seem like it would be very effective.

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