What is the purpose of the perforated ring on a small gas engine piston?

The purpose of the perforated ring on a small gas engine piston is to serve as an oil ring. The oil ring has several critical functions in the operation of the engine. It helps to control the lubrication of the piston and cylinder walls by retaining a small amount of oil that lubricates these moving parts, reducing friction and wear. This is essential to maintain the engine's efficiency and longevity.

Additionally, the oil ring ensures that excess oil does not enter the combustion chamber, which can lead to increased emissions and potential fouling of the spark plug. By performing these functions, the oil ring significantly contributes to the overall performance and reliability of the small gas engine.