The basic job of the clutch is to temporarily disconnect the engine from the transmission and drivetrain system which drives the rear wheel. Unless that happens, it is nearly impossible to mate an idling engine with the transmission and move a geared motorcycle, which is at a standstill, forwards. It is possible to shift gears without the clutch when the bike is moving, but the result isn’t always smooth and if performed incorrectly, the grinding can even damage the gearbox for good.