Tutorial: Repairing and Replacing Harley-Davidson Clutch Plates

A little theory

A vehicle's clutch is the component that connects the engine to the transmission, allowing the force (torque) coming from the engine to be connected or disconnected to the transmission, in order to change gears, for example.

It has one or more friction discs, pressed by springs (or a diaphragm) that are released when we press the lever, thus leaving the engine disconnected from the transmission, which is known as disengaging the engine.

In most motorcycles, the clutch consists of several friction discs (connected to the engine), interspersed with metal discs (connected to the transmission), all bathed in oil. The friction discs are usually coated with aramid, Kevlar, or carbon fiber, to prevent them from slipping on the metal discs when they are pressed by the springs (with the engine engaged).

This material wears out over time and can deteriorate due to excessive heat, losing its effectiveness and allowing the discs to slide against each other even under the force of the spring, a situation in which we say the clutch is slipping.

Diagnosis

We often encounter a motorcycle that revs up when we accelerate, but the vehicle's speed doesn't increase accordingly. In extreme cases, we engage first gear and when we release the clutch lever, the motorcycle doesn't move forward. In both situations, we likely have a worn or damaged clutch.

Tip: If you suspect a slipping clutch, you can back the bike up against a wall and, after shifting into first gear, accelerate gently toward the wall. The RPMs shouldn't rise too much; if they do, the clutch is slipping.

Changing clutch discs

In this tutorial, we're going to replace the clutch plates on a Harley-Davidson Sportster. The first thing we'll do is drain the oil from the primary sump (this model contains both primary and transmission oil).

and loosen the primary chain tensioner.

After removing the footrest support and the gear lever, using a 27mm Torx wrench, loosen the clutch cover screws, allowing access to the ramp mechanism. Using a flat-blade screwdriver, loosen this mechanism until the ramp is released, allowing you to remove it.

We continue loosening all the bolts holding the primary chain cover and then we can separate it from the crankcase.

The next step requires the use of a clutch spring compressor, a tool specific to the year and model of the vehicle we are working on, and which will allow us to compress the diaphragm (spring) to release the retaining clip that holds it.

Using a pair of thin screwdrivers or hooks, we remove the clutch discs one by one while checking and cleaning everything.

Improving the original

A special feature of some Sportster models is that they feature eight friction plates and six steel discs, and a riveted double disc located in the middle to smooth out operation. This disc often breaks easily, destroying the other clutch components.

To prevent this problem and simultaneously increase clutch efficiency, we're installing an "extra plate" kit from the American manufacturer Barnett. This kit eliminates this spring-loaded disc and replaces it with two more, increasing the friction surface area by 12% and improving both grip and component life.

Similarly, we'll replace the small clutch release bearing, which bears all the pressure when the engine is disengaged. This is a very inexpensive component that should be replaced with every disc change.

Mounting

After having the friction discs submerged in oil for a couple of hours, we begin by installing one of these, followed by a metal disc. We then install another friction disc, a metal one… and we alternate them until they are all in place.

We replace the pressure plate and its retaining clip, and we can now release the spring compression tool. At this point, we take the opportunity to remove the clutch release mechanism.

and change the bearing for a new one, we will use a bearing installer and a press or vice.

Now we can install a new gasket and replace the clutch cover, taking care not to damage the gearshift shaft seal. It's recommended to replace this seal, so we'll use a complete primary seal kit when performing this type of operation.

We screw on the cover in the order and to the torque indicated in the service manual for the year and model of the motorcycle we're working on (remember to consult the manual; it's the most important tool). After fully compressing the clutch cable tensioner, we reinstall the ramp mechanism and replace the clutch cover.

At this step we can fill with oil, the Sportster model uses 1 quart (946mL) of specific oil for primary and transmission.

Next, we retighten the primary chain and install the inspection cover by tightening the screws to their corresponding torque (all these procedures are detailed in the manual corresponding to each model).

All that remains is to adjust the clutch cable tensioner. To do this, we will extend the adjuster until the cable has approximately 3 mm of slack.

This clearance is necessary to allow for the expansion of the clutch components as they expand due to heat; if we do not allow it, the clutch discs will burn out prematurely.

Filming

After assembly, we must perform a test ride, checking for proper clutch operation and the absence of oil leaks. It's recommended to run the clutch briefly, without sudden acceleration or deceleration, in the first few kilometers to ensure the components seat properly, thus prolonging their lifespan.

Frank Burguera

#harleymechanics