Piper Comanche PA-24 Service Manual page 433

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PIPER COMANCHE SERVICE MANUAL
d. When the idling speed has been stabili7.ed. move the cockpit mixture control with a smooth. steady
pull toward the "Idle Cut-OFF"' position and observe the tachometer for any change during the "Ieaning
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 "Ieaning out"
indicates an excessi,ely rich idle mixture An immediate decrease in RPM (if not preceded by a momentary
increase) indicates the idle mixture is too lean.
e. 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. 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 abo\"e
method aims at a setting that will obtain maximum R PM with minimum manifold pressure In case the
setting does not remain stable. check the idle 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
7-38. Ignition System.
7-39. Magneto.
CAUTIO"
Ascertain that the primary circuits of both magnetos are grounded
before working on the engine
7-40 Inspection
or
Magnetos. At time of engme inspection or when a magneto has been remO\ed from
the engine. the following checks may be performed. Each step in the check list is keyed by number to a
part shown in Figure 7-8
a Inspect distributor block contact springs If broken or corroded. they should be replaced
b
Inspect oil felt washer. It should be saturated with oil. If dry. check for worn bushing Of 0 K . add
"0.
30 oil
c Inspect distributor block for cracks or burned areas The wax coating on the block should not be
removed Do not use sol\"ents
d. Look for excess oil in breaker compartment If present. it may mean a bad oil seal or oil seal
bushing at drive end Check manufacturer's O\erhaul procedure
e. Look for frayed insulation or broken wire strands in leads in back of magneto. See that termmal,
are secure Be sure wires are properly positioned The position of the leads in the 200 series breaker
compartment must be as shown in Figure 7-9. otherwise chafing or breaking may result
f Inspect capacitor visually. If possible test for leakage. capacity and series resistance Remember. an
electrical failure of an aircraft capacitor is rare
g. Adjustment of breakers must be correct for proper internal timing of magneto (Refer to
paragraph 7-42 )
h Check if breaker cam is clean and smooth. if cam screw is tight (25 in Ibs) If new points are
installed. blot a little oil on cam.
ISSUED: 8/18/72
2B7
POWER PLA'\T