To provide an accelerating pump jet having plural discharge holes delivering to plural directions and having a small diameter capable of achieving sufficient mixture of air and fuel and enhanced vaporizing efficiency in view of conventional problems that a double-barrel type one stage carburetor is produced for a purpose of a race, high output is given a priority and drivability at low/intermediate speed is not regarded as important, but the double-barrel type one stage carburetor is mounted in an ordinary vehicle nowadays and is widely used in an ordinary road and a circuit, and improvement of response and drivability at low/intermediated speed is required, which is considerably affected by an accelerating pump system as auxiliary fuel, discharge hole of a pump jet as delivery port thereof is a single hole having a large diameter and therefore mixture of the air and the fuel is not sufficient, and breathing (accelerating failure) or deterioration of response occurs even when a suitable amount is delivered.

The conventional accelerating pump jet is removed, and is replaced with this pump jet having the delivery port area in suitable quantity and having the plural discharge holes for delivering to the plural direction.