The influence of carburetor characteristics on power, emissions, lean misfire limit and EGR tolerance has been investigated using a single-cylinder engine. The results, which are based on the use of a conventional carburetor and a modified version of the same carburetor, indicate that the lean limit and EGR tolerance are extended when time variations in fuel flow (“spiking” of A/F) are reduced and the mixture is made more homogeneous. The amount of extension varies with engine load, being largest at the lighter loads studied. Power, CO and NOx emissions of the engine are insensitive to the carburetion effects at common values of engine air flow rate and A/F. The HC emissions are affected at all but the richest A/F values investigated.