FUEL AND LUBRICATION SYSTEM 4-7
AIR CONTROLE VALVE
• The air control valve changes the valve opening area to adjust the air volume for slow system in accor-
dance with temperature variation, thereby supplying the optimum air/fuel mixture for idling operation.
In this system, air is taken in from the clean side of air cleaner and guided into the slow system through the
air control valve.
Air supplied both from the slow air jet and the air control valve is metered by the pilot screw to produce air/
fuel mixture most appropriate for the current atmospheric temperature, and then jetted into the main bore.
When temperature is low (air density being high):
• The thermo-wax inside the air control valve shrinks and the
valve opening area is narrowed due to spring force.
When temperature is high (air density being low):
• The thermo-wax inside the air control valve expands causing
the piston to push the valve resulting in widened opening area.
Air density being high
Air density being low
Spring
Valve
Piston
Left air
cleaner box
Air cleaner element
Air control valve
Pilot screw
Slow jet
Slow air jet
AIR
FUEL/AIR MIXTURE
FUEL
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