5.7
Section 5
Fuel System and Governor
5
Adjust Carburetor (Adjustable Main Jet)
1. With the engine stopped turn the low and high
idle fuel adjusting needles in
(clockwise)
until
they bottom
lightly
.
NOTE:
The tip of the idle fuel and high idle fuel
adjusting needles are tapered to critical
dimensions. Damage to the needles and
the seats in carburetor body will result if
the needles are forced.
2.
Preliminary Settings:
Turn the adjusting needles
out (counterclockwise)
from lightly bottomed to
the positions shown in the chart.
CH11
CH12.5
CH14
Idle
High Speed
1-1/4
1-1/2
1-1/4
1-1/2
1-1/4
1-3/4
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. Check that
the throttle and choke plates can fully open.
4.
High Speed Fuel Needle Setting:
Place the
throttle into the “fast” position. If possible place
the engine under load. Turn the high idle fuel
adjusting needle in (slowly) until engine speed
decreases and then back out approximately 1/4
turn for best high-speed performance.
5.
Low Idle Speed Setting:
Place the throttle control
into the “idle” or “slow” position. Set the low
idle speed to
1500 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 1500 RPM. To ensure best
results when setting the low idle fuel
needle the low idle speed should not
exceed 1500 RPM (± 75 RPM).
6.
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 1/8 to 1/4 turn to obtain the best
low speed performance.
7. Recheck the idle speed using a tachometer.
Readjust the speed as necessary.
Adjust Carburetors Only
