Kohler Courage SV710-740 Service Manual page 148

For the engine to be Tier III compliant, it may be fitted with a secondary air induction system (SAI).
Operation: The intake pulse of the engine activates the secondary air valve. Air is drawn through an inlet screen
of the secondary air valve. The air is then drawn into the exhaust manifold and muffler where it mixes with any
unburned hydrocarbons, which then burn in the heat of the muffler. A hose is connected between a carburetor
port and a diaphragm chamber in the secondary air valve. The carburetor vacuum moves the diaphragm to close
the valve when air induction is not required, primary idle. See Figure 11-2.
Maintenance: The air inlet screen in the secondary air valve can be removed, cleaned, and reinstalled. If
inspection of the system reveals any damage or decomposition of the hoses, secondary air valve, or exhaust
system, the parts should be replaced.