Kohler COMMAND CH18, Service Manual

Page: 38 / 232

5.5
Section 5
Fuel System and Governor
5
Carburetor
General
Engines in this series are equipped with Keihin fixed
main jet carburetors. CH18-740 engines use a one-
barrel carburetor. Most applications use a fuel shut-
off solenoid installed in place of the fuel bowl
retaining screw, and also contain an accelerator
pump. All carburetors feature a self-relieving choke
like or similar to the one shown in the exploded view
on page 5.10. CH750 engines use a Keihin BK two-
barrel carburetor on a matching intake manifold. This
carburetor with related servicing and adjustments is
covered beginning on page 5.11.
WARNING: Explosive Fuel
Gasoline is extremely flammable and its vapors can explode if
ignited. Store gasoline only in approved containers, in well
ventilated, unoccupied buildings, away from sparks or flames.
Do not fill the fuel tank while the engine is hot or running,
since spilled fuel could ignite if it comes in contact with hot
parts or sparks from ignition. Do not start the engine near
spilled fuel. Never use gasoline as a cleaning agent.
Troubleshooting - Carburetor Related Causes
Condition
Possible Cause/Probable Remedy
1. Low idle fuel mixture (some models)/speed improperly adjusted.
Adjust the low idle speed tab, then adjust the low idle fuel needle.
1. Engine starts hard, runs roughly
or stalls at idle speed.
2. Engine runs rich (indicated by
black, sooty exhaust smoke,
misfiring, loss of speed and power,
governor hunting, or excessive
throttle opening).
2a. Clogged air cleaner. Clean or replace.
b. Choke partially closed during operation. Check the choke lever/
linkage to ensure choke is operating properly.
c. Low idle fuel mixture is improperly adjusted. Adjust low idle
fuel needle (some models).
d. Float level is set too high. Separate carburetor air horn from
carburetor body, adjust float to specification.
e. Dirt under the fuel inlet needle. Remove needle; clean needle and
seat and blow with compressed air.
f. Bowl vent or air bleeds plugged. Remove low idle fuel adjusting
needle. Clean vent, ports, and air bleeds. Blow out all passages
with compressed air.
g. Leaky, cracked or damaged float. Submerge float to check for
leaks.
3. Engine runs lean (indicated by
misfiring, loss of speed and power,
governor hunting or excessive
throttle opening).
3a. Low idle fuel mixture is improperly adjusted. Adjust low idle
fuel needle (some models).
b. Float level is set too low. Separate carburetor air horn from
carburetor body, adjust float specification
.
c. Idle holes plugged; dirt in fuel delivery channels. Remove low
idle fuel adjusting needle. Clean main fuel jet and all passages;
blow out with compressed air.
4. Fuel leaks from carburetor. 4a. Float level set too high. See Remedy 2d.
b. Dirt under fuel inlet needle. See Remedy 2e.
c. Bowl vents plugged. Blow out with compressed air.
d. Carburetor bowl gasket leaks. Replace gasket.