Main Clutch Spring The Main Clutch Spring helps the the clutch shaft to engage and disengage the clutch on most 48cc and 66/80cc motorized bike engine kits Installation requires advanced skills; do not attempt to disassemble the motor down to the shaft without professional knowledge. It is locked in by ferrules on the clutch shaft, which is located deep within the motor. Take those off, remove the old spring, install the new, reinstall the ferrules, and reassemble the engine