K&S Technologies Carburetor Air Cut-Off Valve Set 56-1004 Direct OEM-style replacement carburetor air cut off valve set Include diaphragm, spring and O-ring Located on the side of the carburetor the air cut off valve prevents lean fuel mixture (backfire) when decelerating Temporarily closes the pilot jet airway to provide a richer mix as the throttle closes Sold in sets for one carburetor