The development history of a 30cc 2-stroke engine power unit in the covered rear wheel for retrofit into standard bicycle chassis. The rear wheel acts as cooling fan for the air cooled long stroke engine with catalyst exhaust system, autochoke carburetor, autolube oil pump, electric start and inertia start, single speed automatic transmission and 7 speed hub final drive. The space in the rear wheel contains intake air filter, exhaust system, fuel tank, oil tank and engine with drive train, the complete engine being only 94mm wide. The complete covered power unit is nearly undetectable as the rear wheel covers resemble road racing bicycles. There is very low stationary and pass-by noise (64 db[A]), no exhaust gas opacity or smell, very low vibration level and very good fuel economy up to 133 km/l. The paper highlights the development steps such as layout and design, acoustic & NVH analysis, FE analysis of stressed parts and acoustic features, thermodynamic layout and the development steps on the dynos.