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Figure 9.
7. Recheck the idle speed using a tachometer.
Readjust the speed as necessary.
Walbro Carburetor Adjustment
In general, turning the adjusting needles in (clockwise)
decreases the supply of fuel to the carburetor. This
gives a leaner fuel-to-air mixture. Turning the
adjustment needles out (counterclockwise) increases
the supply of fuel to the carburetor.
Kohler Adjustable Jet
Low Idle Main Fuel
KT19 1 turn 2-1/2 turns
KT17 1 turn 2-1/2 turns
Figure 10.
NOTE: The tip of the low idle fuel and main 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.
1. With the engine stopped, turn the adjusting
needle(s) in (clockwise) until it bottoms lightly.
2. Preliminary Settings: Turn the adjusting
needle(s) out (counterclockwise) from lightly
bottomed as follows or to the rich side of
adjustment.
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, 6, and 7).
4. Main Fuel Needle Setting: This adjustment is
required for adjustable main jet carburetors only. If
the carburetor is a fixed main jet type, refer to
Walbro adjustment.
Turn the main fuel adjusting needle out
(counterclockwise) from the preliminary setting
until the engine speed decreases (rich). Note the
position of the needle.
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.
Set the adjusting needle midway between the rich
and lean settings.
5. 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 1500 RPM.
6. Low Idle Fuel Needle Setting: Place the throttle
into the idle or slow position.
Turn the low idle fuel adjusting needle out
(counterclockwise) from the preliminary setting
until the engine speed decreases (rich). Note the
position of the needle.
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.
Set the adjusting needle midway between the rich
and lean settings.
Lean
Rich
Adjust to
Midpoint
Low Idle Speed
Adjusting Screw
Low Idle Fuel
Adjusting Needle
Main Fuel
Adjusting Needle
(Adjustable Jet
Carburetor Only)