The Swing has a real clutch, in the rear driven assembly. It is a centrifugal clutch with 5 friction pads or shoes. The clutch slips until the drive belt turns the clutch arms and shoes with enough centrifugal force to lock the whole clutch/driven assembly together. Springs are built into the clutch to disengage it when the rpm drops and to allow the clutch to lock up gently. Clutch slip depends on the rpm of the belt, the weight of the bike and its passengers, road and wind resistance, etc. With very light throttle and light load, the clutch locks at about 20 kph. With large throttle input and heavy load, the clutch may not lock until 50 - 80 kph. If the clutch is glazed or worn, it may not lock at all, and when you accelerate, the engine speeds up but the bike doesn't.