Jeff:
There should be a terminal sticking up on the top of the coil. If you were to short that terminal to the side of the motor, it would shut the motor off. Put a switch in between and mount it to the sde of the fuse and your good to go. You won't get a jolt out of that terminal as it's low voltage. Use a slide switch like your reciever switch. The toggle switches can't take a joke as far as vibration goes. When you turn the motor backwards, can you feel a spring trying to turn it forward?? Most Quadras had a starter spring in the back of the motor where you turn the motor backwards for half a turn and let it go. I don't know it the Byrodrive had that. Made starting a lot easier on the arm.