The Orbital Combustion Process (OCP) has been successfully implemented on automotive and marine engines. Large marine outboards are in production using this technology for emissions control and a limited release of vehicles is underway. ULEV emissions have also been measured in independent laboratories on the automotive engine.The fuel injection system has been adapted to 50cc scooters. Although the same basic injector has been retained, the remainder of the system has been optimized for the different cost, engine size and emission constraints applicable to this market. The system utilizes a crankcase pressure actuated positive displacement metering system with a much simplified control system compared with marine and automotive systems. The basic scooter system has been previously described in SAE 9416871.The combustion process is substantially changed from that used on the larger automotive engines due to the smaller bore size and higher engine operating speed.Optimization of the combustion chamber and injection system for both maximum power and minimum emissions is discussed, including modifications to the cylinder head and piston design, and injector spray requirements. Typical air to fuel ratios and parameter timings are also presented.The resultant misfire free scooter engine demonstrates similar power, reduced fuel consumption and compliance with emission regulations at low incremental cost to the vehicle manufacturer.