This paper presents work performed to improve an engine's fuel economy by introducing ultrasonic atomization as the method of fuelling. An ultrasonic atomizer was added to the air intake path of a four stroke spark-ignited two-wheeler engine, replacing the conventional carburetor.Test results indicate that the engine BSFC reduced by around 20% due to lower pumping losses and lean operation facilitated by better fuel atomization. Less throttling also reduced the pressure difference between the air filter and combustion chamber, especially at lower speeds and low loads. This reduced exhaust gas dilution into the intake manifold and hence a rich mixture was not required for stable operation even at idling conditions. HC emissions are seen to be high and will need to be addressed, but NO emissions reduced significantly.