5.5
Section 5
Fuel System and Governor
5
Low Idle Speed Setting
1. Start the engine and run at half throle for 5 to 10
minutes to warm up. The engine must be warm
before doing step 2.
2. Low Idle Speed Seing: Place the throle
control into the idle or slow position. Set the
low idle speed 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 seing the low idle fuel needle, the
low idle speed must not exceed 1500 RPM
(±75 RPM).
Low Idle Mixture Adjustment*
NOTE: Engines will have fixed idle (no adjustment
possible) or a limiter cap on the idle fuel
adjustment needle. Step 2 can only be
performed within the limits allowed by the
cap.
1. Start the engine and run at half throle for 5 to 10
minutes to warm up. The engine must be warm
before doing step 2.
2. Low Idle Fuel Needle Seing: Place the throle
into the idle or slow position.
Turn the low idle fuel adjustment needle out
(counterclockwise) from the preliminary seing
until 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 seings. See Figure 5-4.
Figure 5-4. Optimum Low Idle Fuel Setting.
*NOTE: If the engine is equipped with a governed idle
adjustment (See Figure 5-23), the governor
will compensate for speed changes due to the
low idle mixture adjustment. Disable the
governed idle control by backing out the
governed idle adjusting screw and seing a
fixed idle speed using the idle speed screw
on the carburetor. Make the low idle mixture
adjustment and then reset the governed idle
speed at the adjusting screw.
Lean
Rich
Adjust to Midpoint
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