Check Oil In A Twincam Harley Primary

The primary drive found on a Harley-Davidson Twin Cam 88-equipped motorcycle transfers the rotational energy produced by the motor to the transmission. A special oil bath is held within the primary’s housing, lubricating and cooling the primary belt and clutch assembly. Like the motor and transmission’s oil supplies, the primary fluid must be checked periodically to maintain fluid levels, but also to check for contamination that could reveal bigger problems within the motorcycle. Checking the primary fluid is not difficult, but does require some disassembly of the primary cover. Expect to spend at least 15 minutes on the job.


1. Use a motorcycle service lift to hold the motorcycle securely in an upright position. Place the motorcycle in neutral and start the motor to warm the primary’s oil supply. Stop the motor after three minutes.

2. Use a Torx-27 screwdriver to unscrew the primary’s clutch inspection cover, the large round cover on the rear of the outer primary cover. Pull the clutch inspection cover and its gasket away from the primary cover.

3. Use a flashlight to look into the primary cover through the clutch inspection port. Take note of the primary fluid level in relation to the clutch assembly held within the primary. Ideally, the primary fluid level should be just below the diaphragm springs on the bottom of the clutch assembly.

4. Pour fresh Harley-Davidson primary fluid into the clutch inspection port to raise the fluid level as needed.

5. Use a Torx-27 screwdriver to affix the clutch inspection cover and its gasket to the outer primary cover.

6. Remove the motorcycle from the service lift and lower it onto its side stand.