New 07 kx250f

I bought this bike almost a month ago. It was brand new off the show room floor. I went to go ride it and it has a really bad misfire around 1/4 throttle. Called Ga motorsports and told them about the problem. Took it in last week and had them look at it. Got it back and I had yesterday off and went to test it and rode it up and down the street and it still did the same thing. I looked around the bike and noticed that the tps wasn't hooked up. Took it in today and they said the fixed it now they are going to have to charge me to look at it and that they don't think anything is wrong it sounded fine reving up. I rode it and showed them runs fine when you get on it and idling but if you cruse or get to a speed with no load it starts missing. They told me that you can't cruse dirt bikes. My 05 and my buddies 09 kxf run great no problems at crusing or anything. I'm going on vacation in a a little over a week and need this bike running right before then. The carb has been cleaned and checked by the dealership the first time I took it in. Is there anything that could be wrong? The jetting is stock and the hot start opens and closes right .I live in central cali.

Sounds like you are lean on the pilot circuit. Stock is a #40, I believe. Try a #42, then a #45 if it still is a bad decel pop.

You can get to the pilot jet by turning the gas off, loosening the carb clamps, rotate the carb bowl towards yourself, and loosen the 17mm drain plug on the bottom of the bowl. Gas will drain not worry. Look inside the hole, you will see the main jet, and next to it and deeper in the carb body you will see a small brass jet with a slot for a flat head screwdriver--that is the pilot jet. Be careful not to strip it taking it out, and be careful not to over tighten it when you put it back in. It will have number on the side of it, first assure that it is not clogged, if it is clean or replace it and try it before going to the #42.

More than likely, you are too lean on the pilot circuit. I am sure others will suggest the same once they get a chance to review the OP.

Good luck and have fun.

I dont get a decel pop very much unless I'm going fast and let off but not much at that. My 05 pops more on decel but the 07 just don't run when just at a steady speed.

mine was like that too until I changed out the rusted plug and switched to a 42 pilot and adjustable mixture screw, now I also have the team green suggested main, needle and leak and she runs like a top!

ok when i get it back ill try that setup

Mine did the same thing do not change the 40 pilot jet. Adjust the air screw mixture. Ride... I bought mine from GA Sports brand new. 2007 non current.

You can raise the needle one , make sure it is warmed up good it will go away after a little riding time and then run fine I have 20 hrs on mine now it runs fine , when it is cold!! it pops a little

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