Both two stroke and four stroke engines have their areas of specialization, and either will work fine if used for its intended purpose. Applications that utilize one engine design would rarely do as well with the other.
Four stroke engines use a system of valves to introduce air and exhaust fuel on every other crankshaft revolution. Two stroke engines have ports built into the cylinder walls, which are opened or closed as the piston passes by.
Because they have a power stroke (combustion event) on every crankshaft revolution, two stroke engines tend to have better throttle response and acceleration per pound than four strokes.
Because they do not require a valve-train or heavy duty block, two stroke engines typically weight about half of what an equivalent four stroke does.
Because they allow fresh air to escape through the exhaust port, two stroke engines are significantly less economical than four strokes.
Four stroke engines are used in heavy applications that require a lot of low-RPM torque, like cars and heavy motorcycles.
Four stroke engines have a dedicated oiling system, which makes them far more reliable and longer lived than two stroke engines.
