Abstract: A large, two-cycle, port-scavenging gas engine commonly used for oil field pumping operations includes a mixing section at the intake of the scavenging chamber. Fuel gas flows through a supply line directly into this mixing section in a continuous manner controlled only by a governor valve at the gas inflow line. In contrast, the air intake fluctuates cyclically as the engine piston reciprocates. The present invention is a fuel regulator for such an engine which is a gas inflow control such as found in certain types of carburetors. Thus, the maximum gas inflow is regulated by the governor valve at the inflow line, but the fuel regulator of the gas inflow control restricts the fuel gas inflow to an amount proportional to the air inflow as the air inflow fluctuates.