Flying Horse 48cc/66cc/80cc 2-Stroke Motorized Bicycle Engine Clutch Shaft &ndash; Gas Bike Shaft Replacement The Clutch Shaft houses the clutch pin mandrel for your 2-stroke 48cc or 66/80cc motorized bike engine and is crucial for engaging your motor Installation will require disassembling the entire motor and splitting the crank case. Once split, locate the shaft and uninstall all parts of the shaft and reinstall them on to the new clutch shaft. Seal the crank case and reassemble the engine- then you're ready to ride