As small gasoline engines run on slightly rich mixture, and do not have catalytic converter, their specific fuel consumption and emission values are very high. When the gasoline engines are operated with pure hydrogen NOx emissions increase and the backfire occurs. In this study, a small engine was run with hydrogen at a suitable lean mixture without occurring backfire, and improvements on fuel consumption and emissions were aimed. Performance emissions and cylinder pressures of the engine were measured for hydrogen and gasoline. The specific fuel consumption and NOx emissions were reduced by about 57% and 66%, respectively at hydrogen operation. Moreover the values near zero for CO, CO2 and HC emissions were obtained. The test results showed that the small gasoline engine can operate with pure hydrogen at a suitable lean mixture without any backfire, and provide important improvements in emissions and fuel consumption without using any exhaust control system, electronic ignition system and fuel injection system which increase cost of engine.