JW is right. Most engines run on the low speed needle for 2/3 to 3/4 of the throttle travel. Most engine running issues are actually due to low speed needle settings being off. Adjust the low speed needle some. Sound like you are lean. Turn the needlecounter clockwise 1/8 of a turn at a time untill it idles well and transitions. Be sure to run the engine a full throttle for a few seconds after making any adjustments to clear the crankcase of any puddled fuel. Do your adjustments with the engine off. Good luck with your engine.

Mark Shuman