CARBURETOR

PURPOSE:To make a fuel flow rate at the time of transient in an idle or off-idle range regulable as well as to aim at reduction in NOx content and engine speed drop value, by installing a regulating mechanism varying a positional relationship between a throttle valve and a bypass port, in case of a carburetor having a slow speed system. CONSTITUTION:In case of a carburetor which is equipped with a slow speed system feeding a bypass port 17 and an idle port 18 with fuel by way of a slow jet 15 and a slow passage 16 by the slow fuel passage 14 branched off from a main passage 16, in relation to the bypass port 17, a member 23 is installed in a carburetor body 1 free of slide motion in a direction going across an axis of the port 17 at right angles. This member 23 is displaced against a spring 24 by rotational operation of an adjust screw 25, and thereby its relative portion to a throttle valve 12 of the bypass port 17 is made so as to be variable. With this constitution, a fuel flow rate at time of transient in an idle or off-idle range is made to be regulable.