Natertater, you are not setting up the mechanical portion correct if the servo is being jammed. You need to properly attach the pushrod on both ends. If the throttle is trying to move beyond it mechanical limits, cut the throw by moving the attach point on the throttle farther out or move the attach point of the push rod on the servo inward; just the opposite if you need more throw. Fortuneately, most modern transmitters also have a way of adjusting the servo throw from one extreem to the other called "end point adjustment" or "ATV" or some other conotation depending on brand of transmitter. In most cases, using the spring to control over ride is not the best way to do it.