Replacing a set of clutch discs is a common motorcycle service. A metric bike technician may be a bit confused when looking at a Harley-Davidson diaphragm spring-type clutch for the first time. Have no worries, it looks a little different, but it works the same way.
Most metric bikes use four to six coil springs to apply pressure to the clutch discs. The pressure applied to the clutch discs allows them to engage and transfer power from the primary drive to the transmission. Pulling in the clutch lever forces the springs to compress and release the pressure on the clutch discs. With the pressure released, the drive and driven clutch discs can turn independently of each other, resulting in a disconnect between the primary drive and transmission.
The diaphragm spring serves the same purpose as the coil springs, but it is a single component. A special tool is usually required to compress the spring for removal and installation. Check the service manual for the specific tools the model may require.
On the Sportster clutch shown in the photos, a Jim’s Tools clutch spring compressor is used. Install the clutch spring compressor to the clutch adjuster screw. Take proper safety precautions as when working with any compressed spring.
Compress the diaphragm spring only enough to remove the spring retaining ring.
Gradually release the spring compressor tool and remove it. Remove the diaphragm spring seat and spring. Check the diaphragm spring for damage and distortion. Replace the spring as needed.
Remove the adjuster screw, retaining ring and adjuster screw assembly.
Lift off the pressure plate to access the clutch discs.
Inspect the condition and thickness of the friction discs. Check the steel plates for warp and discoloration. Replace the clutch discs as a set if the measurements are out of specification or if obvious damage is apparent.
Also, check over the clutch basket fingers and the splines of the clutch hub for damage and wear. If the wear is too great, the clutch discs will not be able to slide and the clutch will not function correctly.
Reassemble the clutch. Make sure to install the diaphragm spring so that the concave side faces the pressure plate. Use new retaining rings and make sure the rings are fully seated in their grooves. The spring compressor will be needed again for installing the diaphragm spring retaining ring.
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