- Purpose (reason): For fun.
- Purpose (as a device): Converting fuel to rotational motion.
- DOHC
- There will be many parts of high accuracy and strength
Generic Engine: Camshaft, Cams, Flywheel, Valve
Simpler Engines: 2-stroke, 4-stroke | OHV, SOHC, DOHC | Steam, Gasoline, Diesel | Linear, Rotary