To the original post. I have a Bobcat 743 from 1985 thats still going. The key is only used to preheat your glow plugs, and start/run. You put the key in the off or central position and pull up on the Red Knob right by your right thigh you stop the engine. I dont think there was too many changes on the 743, not that I am aware of, as they were the original design and was the one that got Bobcat where it is today. If it wasnt for the 743, none of the others would exist. I had to get a new wire harness for mine, and there was no provision for the key to shut the engine off. When you pull up the red knob, if yours is like mine, all it does is shut the air supply off to the engine, basically starving it for air. My sequence for shutting it off, is put key into central position, and pull up on the knob. Once the engine dies, you can either leave the knob up, or push it down, which ever way you want. But the knob will have to be down if you are starting it. Hope that helps you out. Any more questions hit me up, will try my best to answer them.