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• Make sure fuel is reaching the carburetor. This
includes checking the fuel lines and fuel pump for
restrictions or faulty components, replace as
necessary.
• Make sure the air cleaner element is clean and all
air cleaner element components are fastened
securely.
If, after checking the items listed above, the engine is
hard to start, runs roughly, or stalls at low idle speed,
it may be necessary to adjust or service the
carburetor.
Adjust Carburetor
Models CV18-740
NOTE: Certified engines may have a fixed idle fuel
adjusting needle. Do not attempt steps 1 and 2
below. Proceed directly to step 3.
1. With the engine stopped, turn the low idle fuel
adjusting needle in (clockwise) until it bottoms
lightly.
NOTE: The tip of the low idle fuel adjusting
needle is tapered to critical dimensions.
Damage to the needle and the seat in
carburetor body will result if the needle
is forced.
2. Preliminary Settings: Turn the adjusting needle
out (counterclockwise) from lightly bottomed
2-1/4 turns.
3. Start the engine and run at half throttle for 5 to 10
minutes to warm up. The engine must be warm
before making final settings (steps 4, 5, and 6).
4. Low Idle Speed Setting: Place the throttle control
into the idle or slow position. Set the low idle
speed to 1200 RPM* (± 75 RPM) by turning the
low idle speed adjusting screw in or out. Check
the speed using a tachometer.
*NOTE: The actual low idle speed depends on the
application – refer to equipment
manufacturer’s recommendations. The
recommended low idle speed for basic
engines is 1200 RPM. To ensure best
results when setting the low idle fuel
needle, the low idle speed must not
exceed 1200 RPM (± 75 RPM).
5. Low Idle Fuel Needle Setting: Place the throttle
into the idle or slow position. Turn the low idle
fuel adjusting needle in (slowly) until engine
speed decreases and then back out approximately
3/4 to 1 turn to obtain the best low speed
performance.
6. Recheck the idle speed using a tachometer.
Readjust the speed as necessary.
Models with Governed Idle System
An optional governed idle control system is supplied
on some CV18-740 engines. The purpose of this
system is to maintain a desired idle speed regardless
of ambient conditions (temperature, parasitic load,
etc.) that may change. Engines with this feature
contain a small secondary spring connected between
the governor lever and the lower adjustment tab of
the main bracket. See Figure 20.
The system requires an additional procedure for
setting the idle speed. If speed adjustments are
required proceed as follows.
1. Make any necessary speed or control
adjustments following the appropriate
instructions covered in this section.
2. Move the throttle control to the idle position.
Hold the governor lever away from the
carburetor, or hold the throttle lever so it is tight
against the idle speed adjusting screw, to negate
the governor activation. See Figure 21. Check the
speed with a tachometer and adjust it to 1500
RPM.
3. Release the governor lever and allow the engine
to return to the governed idle speed. Check it
with a tachometer against the equipment
manufacturers recommended idle speed.
Governed Idle Speed (RPM) is typically 300 RPM
(approximate) higher than the low idle speed. If
adjustment is necessary, bend the adjusting tab
on the speed control assembly to set. See Figure
20.
Figure 20. Governed Idle Spring Location.
Governed
Idle Spring
Tab