Hi,
  I bought my son a stock 2004 KLX110 to ride.  The bike is completely stock.  In any gear, there is a gigantic flat spot in the throttle.  I got the carburetor rebuilt thinking one of the jets were dirty.  I also changed the plugs, oil and air filter.  The problem still existed.  I then played with the air set screw on the carburetor, and it didn't help at all.  When I pull the choke half way out, the flat spot would disappear, but now the problem is at the low end of the throttle.  How should I fix this?  

Thanks,

Dan

whats the jetting? If its stock it will have a 38 pilot, sounds like you may need to bump up to a 40 pilot jet. Bottom out the fuel screw and turn 1.5 times out to start. Make sure the bike is nice and hot before you start adjusting the fuel screw. www.jetsrus.com