The hole that the throttle lever pin goes through is oblong and has a button on the edge towards the center of the sled. When you push the lever it pushes that button before it starts to pull the cable and everything works how it should. If the throttle sticks and you let go of the lever it releases that button and kills the sled. Some how, probably the tps on the throttle body, it knows if the cable is being pulled. You can test it by starting the sled and pushing the pivot pin towards the outside of the sled with one hand and pushing the throttle with the other, this should kill the sled.
hopefully some of that rambling makes sense.