If the speed does not vary when you move the speed control, the governor is not working properly. Please post a picture of the governor plate, where the speed control cable connects to the speed control lever at the engine end. Most likely something has become bent or dislodged near there. The speed control lever stretches the governor spring, and the air vane has to overcome that spring to limit the engine speed. If the vane is stuck or its link to the throttle butterfly is jammed, for example, the throttle may be open all the time. Do not run the engine until this is sorted out, or you may find part of the connecting rod comes out to join the larger world outside the crankcase.
