Flying Horse 2-Stroke Motorized Bicycle Engine Clutch Woodruff key &ndash; Gas Bike Woodruff Keyway Replacement The Woodruff Key helps the clutch shaft stay in place within your 48cc or 66/80cc bicycle engine kits This key requires advanced skills to install. You will need to disessamble the motor completely, taking off all components, to get to the clutch shaft. From there, install the new woodruff key in place of the old one, reassemble the engine, and you're ready to ride