Case 120 - CARBURETOR ADJUSTMENTS; High Speed Adjustment; Idling Speed and Mixture Adjustment

CARBURETOR
The carburetor has three simple adjustments:
1. High Speed Adjustment
2. Idle Mixture Adjustment
3. Idle Speed Adjustment
High Speed Adjustment
Adjust the high speed screw, Figure 13, by turning the adjusting
screw clockwise (in) imtil the engine misfires or falls off; then turn
the adjusting screw counterclockwise (out) imtil the engine runs
smoothly, approximately two turns.
Place the tractor under load and observe how the engine handles
the load. Loss of power or tendency to stall indicates a lean mix-
ture. Turn adjusting screw counterclockwise not more than 1/8 of
a turn and again try the engine performance. When the high speed
screw is correctly adjusted, it will not be necessary to reset the
carburetor unless load conditions or fuel quality have been radically
changed.
Operating an engine on too lean a mixture causes loss of power
and high exhaust heat.
Figure 13
Idiing Speed and idiing IVIixture Adjustment
Turn the idle mixture screw. Figure 13, counterclockwise ap-
proximately 1-1/4 turns from the closed position. Place the throttle
in 1/2 open position and start engine. With the throttle all the way
up, turn the idle speed adjusting screw. Figure 13, until 1000 RPM
is obtained. The idle mixture screw can be adjusted in or out until
the engine runs smoothly while maintaining 1000 RPM with the.idle
speed adjusting screw.
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