The ignition switch shorts the two wires from the points together to shut the motor off. Since one or the other sets of points is closed at any point in time, one or the other wires to the points is at ground at any one time since the stationary contact is connected to ground all the time through the points mounting frame, so shorting the wires to the two sets of points together, permanently grounds out both sets of points all the time and the motor can’t run. You do not need ground wires at the ignition switch, only a wire to each set of points.
Dave
