Buell S1 Lightning 1996 Manual page 177

Fuel Supply System
See Figure 4-3. Fuel from the fuel tank passes through the
carburetor inlet valve into the carburetor float chamber. The
rising fuel level in the float chamber lifts the float, which in turn
lifts the attached inlet valve closer to the valve seat. When the
fuel reaches the level predetermined by the float level setting,
the float will lift the inlet valve into its seated position, thereby
closing the valve and stopping fuel flow to the float chamber.
AIR
FUEL
AIR/FUEL
4-6
Float
Figure 4-3. Fuel Supply System
www.PlanDeGraissage.org
When fuel is used by the running engine, the fuel level in the
float chamber drops; this lowers the float and inlet valve,
thereby causing the valve to open and the fuel flow to resume.
The float chamber is vented to atmosphere through an air
passage in the carburetor body. The opening for the float
chamber vent passage is next to the carburetor main venturi
inlet, on the carburetor body surface to which the air cleaner
backplate is mounted.
Inlet valve
Drain line
Float bowl
vent
Fuel inlet
(from side)