Trizone - Clutch

The clutch

Motorcycle clutches are like the engines they serve - compact, high performance and highly stressed.

Instead of one large clutch plate they use a series of smaller ones separated by rings with springs squeezing them together. When the clutch lever is pulled the plates are pushed apart allowing them to slip, breaking the power connection between engine and gearbox.

As the lever is released the springs push the plates together again allowing friction to feed power through the gearbox to the road. Whenever that happens, those slipping and gripping plates produce an enormous amount of heat.

So the primary purpose of the oil here is to cool the clutch and to prevent the bending and burning that would otherwise damage the rings and plates.

It’s a delicate balancing act between friction and slip, with the oil caught in the middle. Many modern passenger car oils are formulated for maximum fuel economy that means the oil may contain Friction Modifiers. These additives form a low friction film between the oil itself and the plate and ring surfaces.

This makes it more difficult for the oil to transfer grip through the plates and rings as they engage leading to clutch slip. The driving components spin without transferring all the power through the clutch to the road. The rider may not know why it’s happening, but he’ll know the clutch is slipping because the engine races, but the bike loses acceleration.

If the oil friction is too high the clutch may snatch or grab when engaged giving poor power take up either when pulling away or during gear changes. On the road, grab causes the motorcycle to lurch or jerk as the clutch is engaged.

If the viscosity of the oil is too high the clutch may drag failing to disengage with the lever pulled in. This is a particular problem when the engine is cold and can frequently lead to stalling the bike.

Proper clutch operation is vital for ultimate control and a smooth ride and that all depends on careful oil selection.