The mechanical aspects of a Rotary Valve System (RVS) axe evaluated considering the operating conditions of a single cylinder four-cycle engine. Design of valve geometry, sealing mechanism, and drive mechanism are discussed as well as their impact on the performance of the baseline engine. In order to understand the full capabilities of the RVS, a study of the limitations of the baseline valve train system is performed. This information is then used to establish the minimum requirements of the RVS design. Once the shaft diameter, the port diameter, and the internal shaft passages are determined, the flow is analyzed using a computational fluid dynamics approach. The increased flow of the RVS is expected to increase volumetric efficiency and engine speeds. Even though the RVS is still a concept, when operational it will give four-cycle karters the opportunity to enjoy more powerful engines.