Piper COMANCHE PA-24-180 Service Manual page 424

PIPER COMANCHE SERVICE MANUAL
a.
Turn the engine crankshaft to number one cylinder full advance firing position. (Refer to Figur
7B-13.) Install the magneto on the engine and tighten the mounting clamps sufficiently to hold magneto
position and yet allow it to be rotated
CAUTION
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 "T" 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 WRONG
CYLINDER. It could be on the NEXT cylinder in firing order or it
could be on PREVIOUS cylinder in firing order. 10-720 series
engine firing order is 1-5-8-3-2-6-74
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
NOTE
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 Consequentl,. as the magneto is being timed. the
backlash can be o\erlooked and result in a timing error as much as 6
to 8 degrees To eliminate this possibility. insert a small screwdriver
through the "T" marked opening and engage the painted rotor
timing groo\e (The painted lines on the dstributor block and finger
will be found in approximate alignment.) With a light force depress
the screwdriver. moving the rotor in a counterclockwise direction.
as \iewed from the rear. sufficiently to remove any backlash whileat
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 inaccessabilitv to the "T"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
Repeal this procedure for the other magneto using another timing light
e
After both magnetos have been satisfactorilx timed. leave the timing light wires connected and
recheck timing as previously described to make certain that both magnetos are set to fire simultaneously. If
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