This paper discusses the design, modeling, and development of small motorcycle equipped with a HCCI engine in an series hybrid configuration. A mathematical model was developed using MATLAB/Simulink and used to size the powertrain components and to predict fuel economy. A conventional 125 cc spark ignition engine was modified to run in HCCI combustion mode and integrated into a prototype vehicle. Dual-fuel and external EGR strategies were used to upgrade the engine speed and torque capabilities of the engine to meet the requirements of the powertrain. An electrical generator, hub-motor, battery pack and other power electronics devices were used to form the electrical system for the vehicle. The advantages of the proposed design compared to the original motorcycle with SI engine and CVT transmission are: 1) a reduction in noxious emissions due to the HCCI combustion, and 2) higher fuel economy in city driving because of the HCCI engine and series hybrid powertrain. Fuel economy was measured by driving the motorcycle on a chassis dynamometer using a sequence of ECE-40 driving cycles. The overall fuel economy was measured to be 73.7km/L which represents a 139.3% increase in fuel economy over the baseline vehicle
