Which of the following components is NOT part of a four-stroke engine?

A four-stroke engine consists of several key components that work together in a sequence to convert fuel into mechanical energy. This process involves four distinct stages: intake, compression, power, and exhaust. The piston plays a crucial role as it moves up and down within the cylinder to facilitate these stages. The cylinder houses the piston and contains the combustion process, while the crankshaft converts the linear motion of the piston into rotational motion to drive the vehicle.

The rotor, however, is not a component of the four-stroke engine. Rotors are more commonly found in rotary engines, which operate on a different principle compared to the traditional four-stroke cycle. Therefore, identifying the rotor as a component not part of a four-stroke engine is correct, as it lacks the necessary function and involvement in the operation of this engine type.