The Shovelhead engine was once Harley-Davidson's preferred powerplant and could be found on almost every V-twin-engine motorcycle produced by Harley-Davidson from 1966 to 1984. Although the Shovelhead -- named for the shovel-shaped rocker boxes on the sides of the cylinder heads -- was ultimately phased out by the appearance of Harley's Evolution engine, its design and heritage has attracted a worldwide following. Today, the Shovelhead engine is still available as an aftermarket reproduction; many of the original Harley-built engines, however, are still in service. Unfortunately, older engines often require a complete rebuild to be usable, effectively making it a new engine. Before either type of engine can be placed in active duty, it must be "broken in" to avoid premature engine failure in the future.
Things You'll Need
- Shop fan
- Spark plug socket
- Torque wrench
Park the motorcycle on its side stand and place a shop fan either directly in front or along the side of the engine. Select the highest fan setting and direct the air flow at the engine cylinders.
Pull the spark plug wires off both spark plugs. Follow the spark plug wires to the ignition coil, then unplug the ignition coil from the motorcycle's wiring harness. Unscrew the spark plugs from the cylinder heads, using a ratchet and a spark plug socket.
Remove the top end oil screen plug, on the right side of the engine below the rear cylinder pushrod cover, using a screwdriver or a ratchet. Turn on the ignition and shift into neutral. Push the starter button and hold it in place for five seconds to crank the engine, then release the button. Repeat until oil is visible over the top end oil screen.
Screw the top end screen plug into place. Press and hold the starter button for five seconds to circulate oil throughout the engine, then release the button. Repeat five more times, then turn off the ignition. Screw the spark plugs into place and tighten the plugs to 18 to 28 foot-pounds, using a torque wrench. Push the spark plug cables over the spark plugs, then reconnect the ignition coil to the motorcycle's wiring harness.
Open and close the throttle completely twice to inject fuel into the engine through the accelerator pump, then return the throttle to its fully closed position.
Close the choke and start the engine. Adjust the engine idle speed to 1,200 rpm, using the carburetor throttle stop screw. Open and hold the throttle to increase the engine speed to 2,000 to 2,600 rpm for 15 seconds, then let the engine idle. Stop the engine after two minutes and let it cool for 30 minutes. Repeat this step two or three times.
Take the motorcycle for a short test ride and maintain an engine speed between 2,400 and 3,500 rpm as much as possible. Stay in as low a gear as possible to avoid lugging the engine during the test ride. Avoid congested roads and heavy traffic. Check the engine for oil leaks upon completing the test ride.
Tips & Warnings
- Change your Shovelhead's engine oil after the first 500 miles of use to remove metal shavings and other contaminants created during the break-in process.
- Do not overheat the engine during the break-in process. Excessive heat buildup can permanently damage the engine pistons. Keep a fan pointed at the engine to cool the cylinder heads while the motorcycle is stationary.
- Clymer Harley-Davidson Shovelhead Service and Repair Manual: 1966 to 1984; Clymer
- Shovelhead Engine Owner's Manual; Ultima Motor Works
- Photo Credit Jupiterimages/Comstock/Getty Images