2010 ktm 65 bike hesitates when you give it throttle but when it hits the power band it takes off.

It sounds like moving the main needle clip position may solve this if it's jetted properly. Remove the slide assembly from the top of the carb, pull back the spring and remove the cable. There will be a retainer clip that holds the e-clip and the needle in the slide. Remove that clip and the needle will slide out. Note the original position of the e-clip on the needle, remove it and move it down 1 position. This will raise the needle in the main jet and richen the mixture on acceleration. Reinstall and repeat adjustment until satisfactory acceleration is achieved.
If moving the needle position doesn't solve it, a larger main jet is required. Put the e-clip back to it's original position. Remove the main jet thru the 17mm drain bolt in the bottom of the carb, note the size stamped on it and get the next larger size. A selection of main and pilot jets a couple sizes up and down from stock is always handy to keep around with the 2-strokes as they are sensitve to temperature change.
Always check the condition of the spark plug when making jetting changes. Start with a fresh plug and run it for 10 min at normal riding RPM. Tan is good, black is rich and white is too lean. A lean condition is really bad and must be corrected immediatly. Good luck!