What is a wet multi-plate clutch?

Clutch plate | Driven plate | Friction plate | Oil | Clutch drum | Clutch drag

A wet multi-plate clutch is an assemblage of steel driven plates and compound organic resin friction plates housed in a drum and spinning concentrically on a shaft. With respect to a "wet" clutch, the assembly is cooled by a limited amount of oil. The same basic arrangement/assembly is sometimes used in a "dry" drum; i.e. without being exposed to oil.

Usually, the clutch assembly is composed of six of each type of plate that are alternately stacked (steel, friction, steel, friction, etc; see diagram below). But there might be more or fewer plates (5/5 or 7/7). This configuration is common to both classic bikes and modern bikes.

Wet multi-plate classic bike clutch

It's important to use the correct type of oil, which may or may not be shared with the engine. Take note that if the oil is too thick, or is adulterated with extra lubricants or additives, it can lead to clutch slip. So closely follow the manufacturers recommendations.

Motorcycle clutches are generally easy to remove, refit and fettle. You can expect anything from 10,000 miles to 50,000 miles depending on how you ride and how well the clutch is initially set up. Poorly set-up clutches can drag, chatter or fail to release. Clutches can overheat in traffic if not properly engaged or disengaged. Tip: Don't "ride" the clutch.

The clutch plates are generally engaged/disengaged via a pushrod or some other lifting mechanism. One set of plates engages with the outer drum, and the other set of plates engages with the inner hub. Note the "tangs" on the plates. Springs push the plates together. When held tightly in this way, the assembly "locks" and transmits power from the engine through to the gearbox (transmission). Weak springs, or poorly adjusted spring, can lead to slippage or uneven clutch action (dragging, etc).

Clutches, whether wet or dry, should not be quickly "thrown" together. They need to be carefully (but simply) de-burred and checked for flatness of the plates. Clutch shock absorber rubbers (where fitted) need to be checked and replaced as necessary. Ditto for clutch springs and bearings.

Any reasonably competent person can get to grips (no pun intended) with a classic bike or modern bike clutch. Just take it slowly and, if you feel it necessary, photograph each stage.

Remember to look at our Motorcycle Workshop pages too.
We have more helpful tech tips there.

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