This is a Crankshaft Clamp (Locking Tool) from O.S. Engines. This will work with 91-105 size engine. This device facilitates the installation, or removal, of a flywheel, cooling fan or pilot shaft by temporaily locking the crankshaft so that it cannot rotate. Made of durable plastic, it locks the crankshaft without risk of damage to any part of the engine and can also be used with recoil-starter equipped engines.
How to use: Remove the crankcase rear coverplate from the engine and rotate the crankshaft to the bottom-dead-center position. Insert the crankshaft clamp so that its grooved portion surrounds the crankpin and lower end of the connecting-rod and securely tighten the flywheel, fan or pilot shaft onto the crankshaft. Remove crankshaft clamp when completed and re-install the coverplate back onto the engine.