Piper Arrow IV Turbo Maintenance Manual page 636

ELECTRICAL POWER SUPPLY.
MAGNETO.
Ascertain that the primary circuit of both magnetos is grounded
before working on the engine.
INSPECTION OF MAGNETO.
Comply with the latest revision to Bendix Service Bulletin No.
608 at first opportunity, but not later than next magneto
overhaul. Install self-locking cam retaining screw (P/N 10-
391213) and torque 21-25 inch-pounds. If self-locking screw is
removed at any time, always replace with new self-locking screw
and torque to the specified value.
1. After the first 25 hour and 50 hour periods, and periodically thereafter, the contact assemblies should
be checked. Examine the points for excessive wear or burning. Points which have deep pits or excessively
burned areas should be discarded. Examine the cam follower felt for proper lubrication. If necessary, points
can be cleaned by using any hard finished paper. Clean breaker compartment with dry cloth.
2. If engine operating troubles develop which appear to be caused by the ignition system, it is advisable
to check the spark plugs and wiring first before working on the magnetos.
3. Should the trouble appear definitely associated with the magneto, the most effective measure is to
install a replacement magneto which is known to be in satisfactory condition and send the suspected unit to the
overhaul shop for test and repair.
4. Should this not be possible, a visual inspection may disclose the source of trouble. Remove the harness
outlet plate from the magneto. Inspect for the presence of moisture and foreign matter on the rubber grommet
and high tension outlet side of the distributor block. Check height of block contact springs (0.422 maximum
from top of the block tower to the spring). Also check for broken leads or damaged insulation. If either is
present, remove magneto and replace with one known to be in satisfactory condition.
5. Remove the breaker cover and harness securing screws and nuts, and separate cover from magneto
housing. Check contact assemblies to see that cam follower is securely riveted to its spring. Examine the
contact points for excessive wear or burning. Figure 74-23 shows how the average contact point will look
when surfaces are separated for inspection. Desired contact surfaces have a dull gray, sand-blasted (almost
rough) or frosted appearance, over the area where electrical contact is made. This means that points are worn
in and mated to each other, thereby providing the best possible electrical contact and highest efficiency of
performance.
6. Minor irregularities or roughness of point surfaces are not harmful. (Refer to Figure 74-23, center.)
Neither are small pits or mounds, if not too pronounced. lf there is a possibility of pit becoming deep enough to
penetrate pad, Figure 74-23, right, reject contact assembly.
No attempt should be made to stone or dress contact points.
Should contact assembly have bad points or show excessive wear,
the complete contact assembly should be replaced.
Effectivity
PA-28RT-201
PIPER AIRCRAFT
PA-28RT-201 / 201T
MAINTENANCE MANUAL
—CAUTION—
—NOTE—
—NOTE—
3E8
74-11-01
Page 74-23
Revised: December 21, 1981