Timing refers to the amount of time between the spark plug sparking and fuel ignition.
A shovelhead engine is a V-Twin Harley-Davidson engine that was produced from 1966 to 1985. The name shovel comes from the coal shovel-like shape of the engine covers. When the timing is not correct, the engine can fail. Timing refers to the amount of time that occurs between the spark plug sparking and the fuel in the engine igniting. A timing mark view plug tests engine timing. The view plug flashes a light on the timing tab when the pistons of the engine’s cylinder reach the highest point of the compression stroke.
1. Insert the thread timing mark view plug in the timing inspection hole. Do not touch the flywheel with the plug.
2. Remove the spark plugs. Turn the engine until the front piston is at top dead center on the upward compression stroke of the cylinder piston. Examine the top dead center mark on the flywheel.
3. Connect the leads of the inductive timing light to the front spark plug cable, the positive terminal of the battery, and the ground lead. Check the vacuum hose to make sure that it is connected at the carburetor and the vacuum operated electric switch.
4. Turn the engine on and allow the motorcycle to warm up to normal running temperature.
5. Set the engine’s idle speed by turning the idle adjustment screw, located on the carburetor. Turn it clockwise to increase the speed. Turn it counterclockwise to decrease it. The idle speed should be somewhere between 950 and 1050 RPM.
6. Remove the outer cover pop rivets. Remove the outer timer cover. Remove the inner cover screws, inner cover and gasket. Loosen the timer plate stud bolts a few turns until the sensor assembly can be rotated when you insert a screwdriver into the notch in the plate.
7. Aim the timing light at the inspection hole. Rotate the sensor assembly with the screwdriver so that you can see the front cylinder advance timing mark. Center the mark in the timing inspection hole. Tighten the timer plate studs.
8. Reinstall the gasket, inner cover, inner cover screws and timer cover. Install the new outer cover rivets. Remove the timing mark view plug from the timing inspection hole. Install the hex socket timing plug.