Kohler Command PRO CH620-CH740 Owner's Manual page 34

Fuel System
Troubleshooting-Carburetor Related Causes
Condition
Engine starts hard, runs rough, or
stalls at idle speed.
Engine runs rich (indicated by black,
sooty exhaust smoke, misfi ring, loss
of speed and power, governor
hunting, or excessive throttle
opening).
Engine runs lean (indicated by
misfi ring, loss of speed and power,
governor hunting, or excessive
throttle opening).
Fuel leaks from carburetor.
Fuel Shut-Off Solenoid
Most carburetors are equipped with a fuel shut-off solenoid. Solenoid is attached to fuel bowl. Solenoid has a spring-
loaded pin that retracts when 12 volts is applied to lead, allowing fuel flow to main jet. When current is removed, pin
extends blocking fuel flow.
Below is a simple test, performed with engine off, that can determine if solenoid is functioning properly.
1. Shut off fuel and remove solenoid from carburetor. When solenoid is loosened and removed, gas will leak out of
carburetor. Have a container ready to catch fuel.
2. Wipe tip of solenoid with a shop towel or blow with compressed air to remove any remaining fuel. Take 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 power source is switched OFF. Connect positive power source lead to red lead of solenoid. Connect
negative power source lead to solenoid body.
4. Turn power source ON and observe pin in center of solenoid. Pin should retract with power ON and return to its
original position with power OFF. Test several times to verify operation.
26
Possible Cause
Low idle fuel mixture (some models)/
speed improperly adjusted.
Clogged air cleaner.
Choke partially closed during
operation.
Low idle fuel mixture is improperly
adjusted.
Float level is set too high.
Dirt under fuel inlet needle.
Bowl vent or air bleeds plugged.
Leaky, cracked, or damaged fl oat.
Low idle fuel mixture is improperly
adjusted.
Float level is set too low.
Idle holes plugged; dirt in fuel delivery
channels.
Float level is set too high.
Dirt under fuel inlet needle.
Bowl vents plugged.
Carburetor bowl gasket leaks.
KohlerEngines.com
Conclusion
Adjust low idle speed tab, then adjust
low idle fuel needle.
Clean or replace air cleaner.
Check choke lever/linkage to ensure
choke is operating properly.
Adjust low idle fuel needle (some
models).
Separate carburetor air horn from
carburetor body, adjust fl oat
according to steps outlined in repair
kit installation instructions.
Remove needle; clean needle and
seat and blow with compressed air.
Remove low idle fuel adjusting
needle. Clean vent, ports, and air
bleeds. Blow out all passages with
compressed air.
Submerge fl oat to check for leaks.
Adjust low idle fuel needle (some
models).
Separate carburetor air horn from
carburetor body, adjust fl oat
according to steps outlined in repair
kit installation instructions.
Remove low idle fuel adjusting
needle. Clean main fuel jet and all
passages; blow out with compressed
air.
Separate carburetor air horn from
carburetor body, adjust fl oat
according to steps outlined in repair
kit installation instructions.
Remove needle; clean needle and
seat and blow with compressed air.
Blow out with compressed air.
Replace gasket.
24 690 06 Rev. K