May 30, 2007
problem 1998 kx 125

:uh: I got a riding bud that recently bought a 1998 kx 125 for his kid. The bike keeps fouling plugs, and has problems taking off. It starts fine ,but doesn't like any throttle for a bit until it gets warm. When he tries to take off he has to ride the clutch alot and it sounds like he's trying to start in 4th gear or something. The bike needs to be gone through totally. I'm thinking he needs to fix a dent in the pipe, Clean the power valve, and basically start over with the jetting. Does any of this sound familiar to anybody? Also can someone give me a place to start like correct plug, needle position, main jet, fuel/air screw setting etc? He doesn't have much time to work on bikes and I was just going to take over so any advice would be very much appreciated. Thanks, Mike
Last edited:


Aug 16, 2004
Before touching the jetting make sure everything is in good working condition. Clean the power valve and make sure it isn't hanging open or sticking closed, check the reeds for gaps or chipping/fraying, repack the silencer, clean the carb, check compresion, clean the air filter, etc.

After everything is checked out ok, then start jetting.
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