Piper PA-24 Comanche Service Manual page 422

PIPER
COMA!"olCHE SERVICE
~A~l'AL
a. Turn the engine crankshaft t,o numbe.r one cylinder ful,l advance
firi~g ~osition.
(Refer to
Fi g .
7B-().) Install the magneto on the engine and tighten the mounting clamps sufficiently to hold magneto if.
position and
yet
allow it
to
be rotated.
Extreme caution must be exercised when aligning one of the painted
lines on the distributor finger With the painted line on distributor
block. After magneto has been installed on engine. check through
opening marked "1'" to see that these marks (lines) are still properly
aligned. Cam lobes are so close together that if the magneto is turned
only slightly it will be possible to time magneto on the WRO:\G
CYLI:\ DER.
It
could be on the
~EXT
cylinder in firing order or it
could be on PREvlOl'S cylinder in firing order. 10-710 series
engine firing order is 1-5-8-)-2-6-7-4.
b.
Connect a timing light to switch wire (shielded capacitor wire) and to a good ground on
engine.
C.
If the timing light is out (battery operated models). rotate the magneto housing in direction of its
magneto rotation a few degrees until light comes on. Then turn slowly in opposite direction until light goes
out. Secure the magneto in this position.
:\OTE
The magnetic force in the S-700 series magnetos tends to act in the
direction in which the rotor is turned during the timing operation.
This causes the backlash in the magneto drive gears to accumulate in
the same direction. Consequently. as the magneto is being timed. the
backlash can be overlooked and result in a timing error as much as 6
to
to\
degrees. To eliminate this possibility. insert a small screwdriver
through the "T" marked opening and engage the painted rotor
timing groove. (The painted lines on the distributor block and finger
w ill be found in approximate alignrnent.) With a light force depress
the screwdriver. moving the rotor in a counterclockwise direction.
as viewed from the rear. sufficientlv to remove anv backlash while at
the same time. rotate the magneto back and forth in both directions
until the breaker points just begin to open. as indicated by the timing
light. If inaccessability to the "I'" marked hole prevents it from being
used for holding out backlash. the magneto distributor block must
be removed and the magneto rotor utilized for this purpose.
•
d. Repeat this procedure for the other magneto using another timing light.
.:. After both magnetos have been satisfactorily timed. leave the timing light wires connected and
recheck timing as previously described to make certain that both magnetos are set to tire simultaneously. If
ISSl"ED: 8/18/72
2F18
•
POWER PLA:"T