Although regular maintenance is a must for any Harley-Davidson motorcycle, the cost of having the work done by a Harley-Davidson dealer can be more than most people are willing to spend. Doing the majority of the "wrenching" yourself can save you a great deal of money, providing you do the job right. Changing your Harley-Davidson FLH Twin Cam 88's oil is one of the many task well within the reach of most DIYers, requiring only a small amount of know-how. Larger tasks, however, are best suited for trained technicians.
Place the motorcycle on a stand or lift so that it is standing upright. If you do not have access to a stand, enlist the aid of an assistant to hold the bike upright for you.
Drain the engine oil. Locate the engine oil drain plug, which is just forward of the oil sump under the motor, and place an oil pain directly under it. Remove the drain plug with an Allen wrench and allow the oil to drain. Remove and replace the rubber O-ring from the drain plug before reinstalling it on the motor.
Remove the oil filter: Place the oil pan under the oil filter at the front of the motor. Use a strap wrench or appropriate oil filter wrench to loosen the filter, then completely unscrew it by hand. Allow any remaining oil to drain from the motor.
Prime your new oil filter by pouring up to 88.7ml of oil into the filter. Using your finger, rub a small layer of oil onto the filter's mating surface. Screw the filter onto the motor by hand. When it is snug against the mount, hand tighten it another one-half to two-thirds turn.
Refill the engine's oil tank. Pour up to 2.5 quarts of fresh engine oil into the oil tank through the filler neck. Replace the filler cap.
Drain the primary fluid. Locate the drain plug under the primary derby cover and place an oil pan under it. Unscrew the drain plug with an Allen wrench and allow the fluid to drain. Remove and replace the drain plug's O-ring before reinstalling it onto the primary cover.
Refill the primary fluid. Unbolt the derby cover from the primary housing using a Torx driver and pull the cover and its gasket away. Add fresh primary fluid into the primary directly through the derby hole, pouring no more than 1 quart into the primary. The fluid level should be resting at the base of the clutch diaphragm spring. Reinstall the derby cover and its gasket onto the primary case, tightening the mounting bolts with a Torx driver.
Drain the transmission fluid. Locate the transmission drain plug on the bottom of the transmission and place an oil pan under it. Unscrew the drain plug with an Allen wrench and replace the drain plug O-ring. Reinstall the drain plug once the fluid has drained. Add up to 1 quart of fresh transmission fluid through the filler cap on the right side of the transmission.
Wipe away any spilt oil with a shop towel and dispose of the used oils properly.
Quicken the draining process by warming the bike up and removing any filler caps.
Use an oil filter capable of filtering particles as small as 80 microns. An improper oil filter can allow debris to pass into the motorcycle's oil system. Do not begin this task unless you have access to the proper tools. If you cannot obtain these tools, have the work performed by a properly equipped mechanic.