As the owner of a Twin Cam 88-powered Harley-Davidson motorcycle, it is your job to ensure that the engine, primary clutch system and transmission receives regular fluid changes. Unlike a unit-construction motorcycle, which combines its engine and transmission into one assembly that uses a single type of oil, Harley's Twin Cam engine is a separate item from the transmission and clutch. Each system uses its own oil type that needs replacement every 2,500 miles.
Warm up your Harley-Davidson motorcycle to bring its fluids to operating temperature. Start the motor and let it idle for at least 3 minutes, then turn the motorcycle off. Let the oil settle for another 5 minutes.
Unscrew the engine oil drain plug with a 5/8-inch socket and a socket wrench. On Softail models the engine oil drain plug is under the right side of the motorcycle's frame, near the rear wheel. Dyna and Touring models have their oil drain plugs under the transmission housing. Drain the engine oil into an oil pan. Replace the drain plug's O-ring, then screw it into place after the oil has drained. Tighten the drain plug to 18 foot-pounds with a torque wrench.
Unscrew the oil filter from the front of the engine, using an oil filter wrench. Drain any oil trapped within the filter housing into your oil pan. Fill a new oil filter with 20W50 motorcycle oil, then screw it onto the engine by hand until the filter's gasket is touching the filter housing. Tighten the oil filter an additional 3/4 turn by hand.
Unscrew the transmission housing's drain plug, using a 5/8-inch socket. On Softails, the drain plug is found between the rear shocks; Dyna and Touring models have drain plugs under the left side of the engine's oil pan. Replace the drain plug's O-ring, then screw it into place after the oil has drained. Tighten the drain plug to 18 foot-pounds with a torque wrench.
Unscrew the filler plug from the left side of the transmission, using a 3/8-inch Allen wrench. Fill the transmission with 709ml. of Harley-Davidson transmission fluid, using a funnel. Screw the filler plug into the transmission with a 3/8-inch Allen wrench. Tighten the filler plug to 50 inch-pounds with a torque wrench.
Pull the filler cap out of the oil tank. Fill the oil tank with 3 1/2 qt. of 20W50 motorcycle oil, using a funnel. Clean up any spilt oil with a rag, then reinsert the filler cap into the oil tank.
Unscrew the primary housing's drain plug, located beneath the round clutch inspection cover on the left side of the engine, using a T40 Torx driver. Drain the primary's fluid into your oil pan. Replace the drain plug's O-ring, then screw the drain plug into the primary housing with a T40 Torx driver. Tighten the drain plug to 6 foot-pounds with a torque wrench.
Unscrew all five bolts from the primary housing's clutch inspection cover with a T27 Torx driver. Pull the cover and its gasket away from the primary housing. Fill the primary housing with 946ml. of Harley-Davidson primary fluid. Reinstall the clutch inspection cover and its gasket onto the primary housing, using a T27 Torx driver.
- "The Professional Motorcycle Repair Program"; Professional Career Development Institute; 1995
- "Harley-Davidson Service Manual: Softail Models"; Harley-Davidson Motor Co.; 2004
- "Harley-Davidson Service Manual: Dyna Models"; Harley-Davidson Motor Co.; 2004
- "101 Harley-Davidson Twin Cam Performance Projects"; Chris Maida, Mark Zimmerman and Jeff Hackett; 2005