PURPOSE: To perform stable idling and low load operation of an engine in a widely inclining state, in a low speed system independent type membrane type carburetor.

CONSTITUTION: A slow port chamber 22 and an idle port chamber 21 are separately arranged and a manual regulation valve 32 for idling use only is arranged in a communication passage 30. The slow port chamber 22 is arranged in the proximity of the center of a constant fuel chamber 6 and a jet hole 25 for low speed fuel regulation is formed in a plug 24. The influence of a fuel pressure fluctuation during inclination is low and air is prevented from being sucked, and idling is stabilized through two-stage regulation of a flow rate.