US Patent 7014026 Manual/automatic pressure control mechanism for centrifugal clutch

A centrifugal clutch for motorcycles having a cam-actuating mechanism to force a series of clutch plates into clutching engagement at a predetermined speed, a pressure limiting spring assembly limits the axial force transmitted to the clutch members at higher speeds so that the torque transmission characteristics of the clutch are similar to a manual clutch, and a manual override is capable of maintaining the clutch plates in the disengaged position at lower speeds as well as shifting the clutch members out of clutching engagement at higher speeds with relatively low exertion of manual or hand pressure.