Abstract: A fuel control system for use in an internal combustion engine wherein the combustion device thereof comprises a main combustion chamber and an auxiliary combustion chamber provided therein with an ignition plug, the main and auxiliary combustion chambers communicating with each other through a through-hole. A rich mixture of gasified fuel and air is supplied to the auxiliary combustion chamber and a lean mixture of gasified fuel and air is supplied into the main combustion chamber and the mixture in the main combustion chamber is ignited by the flames produced in the auxiliary combustion chamber.

Abstract: A variable stage type carburetor provided with a venturi vane which is adapted to vary the venturi area in a venturi portion thereof, commensurate to the opening of a throttle valve. This carburetor features that, in the running condition where the opening of a throttle valve is considerably large and yet the quantity of intake air is relatively less, the venturi vane is forcedly displaced in a direction to be closed so as to increase the venturi negative pressure in the venturi portion, thereby enhancing the injection of fuel.

Abstract: A secondary air control device which comprises an air passage communicating an air pump with a recombustion device and having a resistor such as an orifice provided midway of the passage and a control valve for maintaining substantially constant the pressure ratio of the pressure on the upstream side of the aforesaid resistor to that on the downstream side thereof, said control valve being so designed as to be operated in association with the pressure of the secondary air and that of exhaust gas, thereby eliminating fluctuation in pressure in the secondary air due to reduction in the discharging performance of the air pump, and thus the secondary air proportional in quantity to the exhaust gas from an engine may be supplied.