Harley-Davidson uses a gear-type oil pump to feed the bearings and bushings in the engine of the 1972 Sportster. The pump supplies low-pressure, high-volume oil flow through the various oil passages within the block, then returns the oil to the oil reservoir. A newly rebuilt engine will not have oil in the bearings or bushings, and the forces generated within the engine by the rotating and reciprocating parts can damage the new bearings and journals. The engine must be thoroughly primed with oil before running.
1. Locate the oil reservoir to the rear of the engine below the seat on the right side of the Sportster. Remove the oil reservoir cap. Fill the oil reservoir to the “Full” mark. Install the reservoir cap.
2. Remove the hose clamp from the oil return hose, at the reservoir end, using the appropriate screwdriver to loosen the clamp. Pull the oil return hose from the return nipple on the reservoir. Lead the loose end of the oil return hose into a clean oil container.
3. Disconnect the ignition coil wires from the primary side of the ignition coil located below the fuel tank and above the engine using a wrench. Place the wires so that they cannot arc to the ignition coil terminals, any part of the frame or engine or each other.
4. Turn the engine over using the ignition switch for 10 seconds. Allow the starter to cool for one minute. Repeat as necessary until oil begins to discharge from the oil return hose.
5. Install the oil return hose onto the oil return nipple on the reservoir. Tighten the oil return hose clamp securely using a screwdriver.
6. Top off the oil in the reservoir to the “Full” mark.
7. Connect the ignition wires to the terminals on the ignition coil using a wrench.