Idle Speed And Mixture Adjustment; Lubrication System; Oil Grades And Limitations; Oil Suction And Oil Pressure Screens - Lycoming O-320 76 Series Operator's Manual

LYCOMING SERIES OPERATOR'S MANUAL
O-320
d. Air Intake Ducts and Filter – Check all air intake ducts for dirt or restrictions. Inspect and service air
filters as instructed in the airframe manufacturer's handbook. Replace any filter or air ducts that shows
signs of deterioration or collapse.
e. Idle Speed and Mixture Adjustment –
(1) Start the engine and warm up in the usual manner until oil and cylinder head temperatures are
normal.
(2) Check magnetos. If the "mag-drop" is normal, proceed with idle adjustment.
(3) Set throttle stop screw so that the engine idles at the airframe manufacturer's recommended idling
RPM. If the RPM changes appreciably after making idle adjustment during the succeeding steps,
readjust the idle speed to the desired RPM.
(4) When the idling speed has been stabilized, move the cockpit mixture control lever with a smooth,
steady pull toward the "Idle Cut-Off" position and observe the tachometer for any change during
the leaning process. Caution must be exercised to return the mixture control to the "Full Rich"
position before the RPM can drop to a point where the engine cuts out. An increase of more than
50 RPM while "leaning out" indicates an excessively rich idle mixture. An immediate decrease in
RPM (if not preceded by a momentary increase) indicates the idle mixture is too lean.
If the above indicates that the idle adjustment is too rich or too lean, turn the idle mixture
adjustment in the direction required for correction, and check this new position by repeating the
above procedure. Make additional adjustments as necessary until a check results in a momentary
pick-up of approximately 50 RPM. Each time the adjustment is changed, the engine should be run
up to 2000 RPM to clear the engine before proceeding with the RPM check. Make final
adjustment of the idle speed adjustment to obtain the desired idling RPM with closed throttle. The
above method aims at a setting that will obtain maximum RPM with minimum manifold pressure.
In case the setting does not remain stable, check the throttle linkage; any looseness in this linkage
would cause erratic idling. In all cases, allowance should be made for the effect of weather
conditions and field altitude upon idling adjustment.

3. LUBRICATION SYSTEM.

a. Oil Grades and Limitations – Service the engine in accordance with the recommended grade oil as
specified in Section 3, item 9, d.
b. Oil Suction and Oil Pressure Screens – At each fifty hour inspection remove, inspect for metal
particles, clean and reinstall.
On installations employing external oil filters, the inspection of the oil suction screen is
impractical at this time, but should be observed when lubricating oil is changed.
MAINTENANCE PROCEDURES
NOTE
SECTION 5
5-5