Since the crankshaft is North-South, it looks like the small sprocket closest to the front wheel is the output from the engine. The pulley between the output sprocket and the chainwheel appears to be for tensioning the chain. It looks like there is a slot in the side cover to move the pulley up or down.

What is that brass wheel at the front of the engine? Notice that it is mounted to a plate.

10.5cc, overhead valves and 10,000 rpms, and 4 stroke. This is like the predecessor to Honda's racing motorcycle and first Grand Prix engine. Perhaps Soichiro Honda would be fan of this engine/bike.

I've would also like to note that Ettore could have created horsepower by just making the engine displacement larger. But he chose this path. Interesting. Was this the prototype for later automobile engines?