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How to Change the Oil on a 1991 Harley Heritage

by Chris Gilliland; Updated November 07, 2017

Items you will need

  • Service stand

  • Flat screwdriver

  • Catch pan

  • Shop rags

  • 3 qts. 20W50 motor oil

  • T-27 and T-40 Torx screwdrivers

  • 1 qt. transmission fluid

  • 1 qt. primary fluid

Basic maintenance for a 1991 Harley-Davidson Heritage Softail Classic motorcycle is fairly simple, often involving the draining and replacement of the motor's oil supply and the fluids used by the transmission and primary drive. Standard practice for the Harley-Davidson is to change the transmission and primary drive fluids along with the oil. Harley-Davidson owners can accomplish this on a weekend afternoon using common hand tools. Warming up the motorcycle and its oil supply can help make the task easier, but take the time to locate the various drain plugs before beginning to prevent burning yourself on the motor's surface.

Motor Oil and Oil Filter

Mount the motorcycle on a service stand to hold it in a vertical position. Locate the oil tank's drain hose on the left side of the frame below the transmission housing. Locate the transmission fluid drain plug under the transmission cover on the left side of the transmission housing. Locate the primary fluid drain plug directly below the round derby cover on the outer primary cover.

Unscrew the oil tank's filler cap. Loosen the oil tank's drain hose clamp with a flat screwdriver and pull the drain plug out of the hole. Drain the oil into a catch pan. Clean the drain hose and its plug with a shop rag. Push the plug into the drain hose and tighten the clamp with a flat screwdriver.

Unscrew the oil tank's filler cap. Loosen the oil tank's drain hose clamp with a flat screwdriver and pull the drain plug out of the hole. Drain the oil into a catch pan. Clean the drain hose and its plug with a shop rag. Push the plug into the drain hose and tighten the clamp with a flat screwdriver.

Fill the oil tank with 3 qts. of fresh 20W50 motor oil. Screw the oil filler cap back onto the oil tank.

Start the motor and check for oil leaks at the oil drain hose and the oil filter. Stop the motor and tighten the drain hose's clamp or oil filter as needed.

Transmission and Primary Fluids

Unscrew the transmission's filler cap. Remove the transmission housing's drain plug with a T-40 Torx screwdriver. Drain the transmission fluid into a catch pan. Clean the drain plug's tip and the drain hole with a shop rag. Screw the drain plug into the transmission housing and tighten it with a T-40 Torx screwdriver.

Fill the transmission housing with 1 qt. of fresh transmission fluid. Screw the transmission's filler cap back onto the transmission housing.

Remove all three bolts from the primary's round derby cover and the primary drain plug with a T-27 Torx screwdriver. Drain the primary fluid into a drain pan. Clean the primary's drain hole and the drain plug with a shop rag. Screw the drain plug into the primary cover and tighten it with a T-27 Torx screwdriver.

Pour fresh primary fluid into the primary cover. Fill the primary until the fluid is just touching the bottom of the clutch basket on the inside of the primary cover.

Place the derby cover onto the primary cover. Tighten all three derby cover bolts with a T-27 Torx screwdriver.

References

About the Author

An avid motorcyclist, Chris Gilliland has immersed himself into the two-wheeled world while balancing work life and raising three daughters. When he is not managing the parts department of a local, multi-line motorcycle dealership, Gilliland can often be found riding, writing or working on his motorcycle blog, Wingman's Garage.

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Photo Credits

  • The dark blue motorcycle stands on road image by Aliaksandr Zabudzko from Fotolia.com