Home › Forum › Ask A Member › RD 19 wiring diagram › Re: RD 19 wiring diagram
OK, in the first place, that motor did not have a kill switch or ignition switch as it came from the factory. So somebody has added that second wire coming from the magneto. That’s good, if you want a kill switch because the wire is already there. To add a kill switch, simply extend that dangling black wire to one side of it and run another wire from the other side of the kill switch to the center post on the vacuum cut-out switch (the mystery thing in your picture). Leave the present wire on that center post and don’t mess with any other wires.
The vacuum cut-out switch senses when the engine is in run-away condition and cuts out the bottom cylinder till it slows back down. The mercury switch lets the vacuum switch do it’s job only at slow throttle settings. If it were allowed to do it at high throttle settings, it could cause a high speed miss. And yes they WILL go into run-away mode without the vacuum cut-out, and you won’t have any way of stopping it, short of taking a hammer to a spark plug.