This rubber coupling sits between the engine and the chopper’s driveline, transmitting torque while absorbing torsional vibration and minor misalignment. It connects the flywheel to the input shaft of the gearbox; the six holes in the coupling body match the bolt pattern on both flanges. A worn or cracked coupling produces a knocking sound at idle and can allow the driveline to run out of balance, leading to bearing wear on the upstream shaft. The original part uses a rubber compound with a specific durometer that matches the damping characteristic the assembly was designed for; a softer compound would let the driveline oscillate at certain speeds, while a harder compound would transmit more vibration into the gearbox. When replacing, clean both flange faces and tighten the bolts in a cross pattern to the torque value specified for the application.