Abstract: A drivetrain including a primary clutch and a secondary clutch is well-suited for use in a single-speed vehicle. The primary clutch may be automatically-engaging or manually-engaging. The secondary clutch, preferably, is normally engaged and is configured to disengage, or slip, at a threshold torque level. Desirably, the slip torque level of the secondary clutch is configured to be greater than the peak engine torque of the vehicle such that disengagement of the secondary clutch due to engine-supplied torque does not occur.

Abstract: A motorcycle clutch having a drive portion including a clutch basket assembly, and a driven portion including a clutch hub. A plurality of drive clutch plates are driven by the clutch basket assembly and a plurality of driven clutch plates are driven by the clutch hub. A pressure plate is coupled for rotation with the drive portion and is capable of axial movement from at least a first position to a second position. A release plate is capable of axial movement from at least a first position to a second position. The pressure plate and release plate are arranged on opposing sides of an alternating arrangement of the frictional and metal clutch plates. A plurality of engagement balls are placed between the clutch basket assembly and the pressure plate. The clutch basket assembly includes a plurality of ramped surfaces configured such that radial movement of the engagement balls results in axial movement of the pressure plate from its second position to its first position to automatically engage the clutch.