Reply To: Johnson HS39 carbon rods and springs

[Mumbles]

Just to elaborate a bit on these alternate firing twin mags, the crank has two cams ground on it with one set of points. When the points open, the current goes from one terminal of the coil to one of the carbon brushes, which is temporarily insulated from the flywheel ground by the Bakelite plate inside it, but connected to one of the spark plug leads. Then it travels to the spark plug, back to ground and returns to the second terminal on the coil via the brass plate which is temporarily in contact with the second carbon brush. This completes the circuit. The brass plate is electrically bonded to the flywheel by a small spring under the plate. As the crankshaft turns 180 degrees, the process repeats itself to fire the other spark plug, but now the opposite carbon brush is insulated from ground, firing the second cylinder.