A Design of experiments methodology was carried out to investigate the effects of the compression ratio, cylinder head material, and fuel composition, on the engine speed, fuel consumption, warm-up time, and emissions of a carbureted single cylinder air-cooled spark ignited engine. The work presented here is aimed at finding out the sensitivity of engine responses, as well as the optimal combination between the abovementioned parameters.Engine performance was evaluated based on the changes in engine speed at idle conditions.Regarding the exhaust gas emissions, the concentrations of CO2, CO, and HC were recorded.