RE: Aurora 9 throttle servo??
Binding can occur at either travel stop peculiar to the linkage and or carburetor end point mechanical stops or; somewhere in the middle too. Simply make sure your not driving the servo past the carb’s end points. An inline servo amp-meter is best for this or reduce end points on the throttle servo throw until you observe some movement.
Generally speaking you want as much resolution as possible with the throttle servos travel arc, most gasser carbs use about 60-80 degrees total throw idle to wide open. Most servos have a travel arc of 120 degrees with 100% travel volume at the TX. As you suggest torque is not an issue with a throttle servo, that said the travel arc is paramount and for best results you need to provide the proper linkage ratio which will allow full servo arm travel (120*) while moving the carb arm 60-80 degrees. Simplest way to get there is to maintain a 50% arm length differential between the two arms, i.e., 1/2” servo arm and 1” carb arm. This allows the servo travel end-point to end-point for the most finite steps or resolution while moving the carb butterfly through its complete travel arc too without over driving the servo into mechanical stops ( if they exist).
If the servo is defective please return it to Hitec Service for warranty repair.