Kohler LH630-775 Service Manual page 31

Section 5
Fuel System and Governor
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Figure 5-2. Valve Cover Torque Sequence.
Carburetor
General
Engines in this series are equipped with emission
compliant fixed main jet carburetors, manufactured by
Keihin. All have self-relieving chokes for efficient
operation. Depending on the specifications and
application involved, most will also contain a fuel
shut-off solenoid and an accelerator pump. An
exploded view of the carburetor is shown in Figure
5-6, with the accelerator pump components shown in
the inset.
Float Circuit: Fuel level in the bowl is maintained by
the float and fuel inlet needle. The buoyant force of
the float stops fuel flow when the engine is at rest.
When fuel is being consumed, the float will drop and
fuel pressure will push the inlet needle away from the
seat, allowing more fuel to enter the bowl. When
demand ceases, the buoyant force of the float will
again overcome the fuel pressure and stop the flow.
High Altitude Operation
When operating the engine at altitudes of 1500 m
(5000 ft.) and above, the fuel mixture tends to get
overrich. This can cause conditions such as black,
sooty exhaust smoke, misfiring, loss of speed and
power, poor fuel economy, and poor or slow governor
response.
To compensate for the effects of high altitude, a special
high altitude main jet can be installed. High altitude
jets are sold in kits which include the jet and necessary
gaskets. Refer to the Parts Manual for the correct kit
number.
5.4
Fuel Shut-Off Solenoid
Most carburetors are equipped with a fuel shut-off
solenoid. The solenoid has a spring loaded pin that
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retracts when 12 volts is applied to the lead. When
power ceases, the spring loaded pin extends and
blocks the main jet.
Below is a simple test made with the engine off that
can determine if the solenoid is functioning properly.
Use a separate, switched 12 volt power supply to test.
2
Carburetor Adjustments
General
In compliance with government emission standards,
the carburetor is calibrated to deliver the correct air-
to-fuel mixture to the engine under all operating
conditions. Both the low and the high speed mixture
circuits are preestablished and cannot be adjusted. The
low idle speed (RPM) is the only adjustment available.
NOTE: Low idle speed (RPM) adjustment should be
1. Shut off the fuel and remove the solenoid from
the carburetor. When the solenoid is loosened
and removed, gas will leak out of the carburetor.
Have a container ready to catch the fuel.
2. Wipe the tip of the solenoid with a shop towel or
blow it off with compressed air, to remove any
remaining fuel. Take the solenoid to a location
with good ventilation and no fuel vapors present.
You will also need a 12 volt power source that can
be switched on and off.
3. Be sure the power source is switched "off".
Connect the positive power source lead to the red
lead of the solenoid. Connect the negative power
source lead to the solenoid bracket.
4. Turn the power source "on" and observe the pin
in the center of the solenoid. The pin should
retract with the power "on" and return to its
original position with the power off. Test several
times to verify operation.
made only after the engine has warmed up.