What is the main difference between two-stroke and four-stroke engines?

Two-stroke engines are designed to complete a full power cycle in just two strokes of the piston, which occurs with one complete rotation of the crankshaft. This design allows for a more compact engine that can produce power more frequently—every revolution of the crankshaft—compared to four-stroke engines, which require four strokes of the piston (two crankshaft revolutions) to complete a full cycle. This characteristic of two-stroke engines contributes to their high power-to-weight ratio, making them popular in applications where performance and size are critical, such as in small motorcycles, chainsaws, and other handheld tools.

Additionally, the operational simplicity of two-stroke engines means they generally have fewer moving parts, which can contribute to lower manufacturing costs and ease of maintenance. Understanding this fundamental characteristic is essential for distinguishing between the two engine types and their applications in various machinery.