Assemble it from hundreds of precision metal pieces and screws. Full instruction manual and parts diagram is included. The crankshaft, pistons, pushrods, valves, chain, etc. all function as on the real engine. An electric power pack base is sometimes available that operates the engine through a throttle twist grip (see the factory-built version). Removable covers and cutaway cylinders to view all internal operations. Long out of production and hard to find. Click any photo to enlarge.