Air-fuel mixture distribution system for multi-cylinder internal combustion engine

In a multi-cylinder internal combustion engine equipped with means for purifying exhaust gases discharged from all the cylinders, the system for supplying during low load engine operation a first air-fuel mixture leaner than stoichiometric mixture into predetermined cylinders and a second air-fuel mixture richer than stoichiometric mixture into the remaining cylinders, and during medium and high load engine operations the first air-fuel mixture into all the cylinders, comprising:

• a carburetor for supplying the first air-fuel mixture into all the cylinders;
• and
• a mixture enriching device arranged to supply supplemental fuel from the fuel chamber of said carburetor into portions upstream of the intake ports of said remaining cylinders to enrich the first air-fuel mixture therethrough into the second air-fuel mixture, said mixture enriching device being arranged to supply the supplemental fuel in response to the engine load only during low load engine operation.