Small gasoline engines are becoming more and more like miniature versions of automotive engines. Today’s larger small engines are utilizing both air and water cooling, carburation and electronic fuel injection. Some even use electronic control modules or “computers.”
From the beginnings of small engines most were what is known as “flat head” engines. This meant that the engine’s intake and exhaust valves were located in the side of the cylinder next to the cylinder bore. Flat head engines worked extremely well for years but were not very efficient.