Torsion Spring clutch shaft Simson

Clutch springs

No matter what kind of clutch is used on your bike (multi-plate wet clutch, centrifugal clutch ...), springs are always needed for clutch engagement. These springs do not all look the same, but they have more or less the same function, namely fot the clutch to engage / disengage.

In multi-plate clutches like those found in supermotos, motocross bikes, and motorcycles with manual transmission, the springs fatigue and shrink over time, and when they eventually become too small, the clutch will slip.
On motocross bikes, you also see diaphragm springs (KTM type) more and more often. In this case, the spring is a sort of large, domed disc. It needs to be replaced when it gets too flat, which also leads to clutch slippage.
There are also dry clutches (Ducati type) that are sometimes found on tuned 50cc bikes. The springs are similar to wet clutches.
On scooters with a centrifugal clutch, the springs will gradually lose tension, making clutch engagement increasingly spongy.