Performance, combustion and emissions investigations relating to the use of gasoline injection in a spark ignition engine are described in this paper. The engine used for experimental purpose is a motorcycle engine of 13.4 kW (18 HP). Experimental engine test setup is designed to operate in carburetion as well as in injection mode [1]. Electronic controlled throttle body injection system is designed to operate test engine in injection mode. This paper also present the procedure used for gasoline fuel injection optimization and discussed the results obtain for minimum fuel consumption, for maximum power and for minimum brake specific fuel consumption, for optimization of the start of injection (i.e. injection delay), injection duration and injection pressure, for the entire operating range, of the research engine used for investigation. All other parameters were noted as observed in carburetion mode test, in addition to that start of injection, injection duration, injection pressure were noted. Similar experimentation was carried out for several injection pressures for gasoline fuel. Performance tests conducted with this system showed considerable performance improvement in power output and in thermal efficiency, as well as substantial reduction in BSFC, HC, CO and NOx emissions, when compared with current carbureted engine and being capable of emitting about half level of the long-term emissions regulation. This paper describes the comparative optimized results, for minimum fuel consumption, maximum brake power and minimum brake specific fuel consumption (BSFC); those were obtained by conducting constant speed tests at various engine speeds and throttle positions, in injection mode. This paper also presents the comparative results of fuel consumption, brake power, BSFC and emissions obtained while carburetion and injection version for constant speed test at 3000 RPM engine speed. The results of this work can contribute to improve the air pollution in the urban area.