Above is a diagram of a circuit to kill the engine, if you loose oil pressure. I got the idea from the BTW Forum, but I couldn't make it work by just wireing the sw. to the coil. The light would stay on all time, due to the points grounding each time the coil charged. I used 3 amp diodes, I got from Radio Shack. They have bands around one end and this indicated the cathode end. That is the same as the cross mark, ahead of the arrow, on the print. they must be wired in this direction. I used male and female quick slides on mine, If a diode goes bad I can just unplug the unit and plug it up like it was orrigionally. The draw back is the diode might open up and not kill the motor, but a bulb could blow also. This way you have two chances at stopping the engine if you loose oil pressure. Below is a picture of the unit mounted on my trike. If you have any questions, email me at halliburton@nctc.com.