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4. Low Idle Speed Seing: Place the throle 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 the equipment
manufacturer’s recommendations. The
low idle speed for basic engines is 1200
RPM. To ensure best results when seing
the low idle fuel needle, the low idle
speed should be 1200 RPM
(± 75 RPM).
5. Low Idle Fuel Needle Seing: Place the throle
into the idle or slow position. Turn the low idle
fuel adjusting screw 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 and
readjust the speed as necessary.
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An optional governed idle control system is supplied
on some 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 5-7.
The system requires an additional procedure for
seing 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 throle control to the idle position.
Hold the governor lever away from the
carburetor, or hold the throle lever so it is tight
against the idle speed adjusting screw, to negate
the governor activation. See Figure 5-8. Check
the speed with a tachometer and adjust it to 1500
RPM.
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2. Preliminary Seings: Turn the adjusting screw
out (counterclockwise) from lightly boomed
2-1/4 turns.
3. Start the engine and run at half throle for 5
to 10 minutes to warm up. The engine must be
warm before making final seings. Check that the
throle and choke plates can fully open.
NOTE: If the carburetor has a self-relieving choke,
the choke plate and sha assembly is spring
loaded. Check to make sure the plate moves
freely and is not binding, affecting idle fuel
delivery.
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NOTE: The tip of the idle fuel adjusting screw is
tapered to critical dimensions. Damage
to the needle end and the seat in the
carburetor body will result if it is forced.