| 摘要 |
PURPOSE:To ensure high purifying efficiency of exhaust gas with use of a low priced carburetor, by fixing flow resistance in an air bleed passage so that air fuel ratio is periodically changed within a specific value for an averaged value. CONSTITUTION:Size of the first air bleed jet 37 and the second air bleed jet 38 is fixed such that an averaged value of air fuel ratio A/F of a mixture supplied to an engine cylinder is arranged to almost theoretical air fuel ratio when a valve port 53 is repeatedly opened and closed by a valve body 54 of a solenoid valve 50, and a change width of the air fuel ratio is within almost + or -0.2-+ or -1.0 for the theoretical air fuel ratio. The air fuel ratio of the mixture fed into the engine cylinder is changed in a 1Hz-2Hz frequency within a range of almost + or -0.2-+ or -1.0 with respect to the theoretical air fuel ratio, and an oxygen holding function of a ternary monolithic catalyst 5 is utilized then high purifying efficiency is obtained.
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