Cub Cadet 1405 - Page 19

To Adjust Carburetor
1. W ith the engine stopped, turn the low idle fuel
adjusting needle in (clockwise) until it bottoms
lightly.
Now turn the adjusting needle in (clockwise).
The engine speed may increase, then it will
decrease as the needle is turned in (lean). Note
the position of the needle.
■ ^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 Low Idle Fuel Needle Setting:
Turn the adjusting needle out (counterclockwise)
from lightly bottomed 1 full turn.
3. Start the engine and run at half throttle for five to
ten 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 con¬
trol 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.
5. Low idle Fuel Needle Setting: Place the throt¬
tle into the "idle" or "slow" position.
Turn the low idle fuel adjusting needle out (coun¬
terclockwise) from the preliminary setting until
the engine speed decreases (rich). Note the
position of the needle.
Set the adjusting needle midway between the rich
and lean settings. (Refer to Figure 21.)
ADJUSTMENT LEAN
Figure 21. Optimum Low Idle Fuel Setting
NOTE
The actual low idle speed depends on the
applicatiorv-refer to equipment manufac¬
turer’s recommendations. The recom¬
mended low idle speed for basic engines is
1200 rpm. To ensure best results when set¬
ting the low idle fuel needle, the low idle
speed must not exceed 1500 rpm.
6. R echeck the idle speed using a tachometer.
Readjust the speed as necessary.
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