Piper Navajo Chieftain PA-31-350 Service Manual page 484

NAVAJO CHIEFTAIN SERVICE MANUAL
h.
Install the magneto to engine gasket on the magneto flange.
i. Feel the magnet into its number one neutral position as described in Step g. With the engine in its
recommended number one cylinder firing position of 20 BTDC, place the magneto in position on the
engine mounting pad and secure with the flange clamps finger tight.
j.
Install short adapter leads made from Bendix terminal kit (part number 10-382698) into magneto
switch terminals and connect to Bendix timing light (part number 11-9110) or equivalent.
k. Bump the magneto in the direction opposite the normal shaft rotation until the first breaker
opens. Due to normal tolerances, one breaker may open slightly before the other and timing should be done
to the first or early breaker. Evenly tighten the magneto mounting clamps.
1. When the final timing check is done, back the engine up approximately 10 degrees; then carefully
bump the engine forward and observe the position that the breakers open. The first breaker should open at
the number one engine firing position and the late breaker must open within 3 engine degrees from the first
breaker opening. It makes no difference which breaker opens first.
m. Repeat Step k if necessary until conditions of Step 1 are met. If the late breaker opens more than 3
degrees from the early one, the internal timing of the magneto must be rechecked. (Refer to Internal Timing,
Paragraph 8-75.)
n.
Torque the magneto securing clamps to 150 inch-pounds. Recheck timing once more and it
satisfactory disconnect the timing light and remove the adapter leads.
o.
Reinstall the plugs in the timing inspection holes and torque to 12-15 inch-pounds. Loosely
install the harness with clamps and/or brackets. Reinstall the air pressure line to the adapter fitting at the
one end of the magneto housing.
NOTE
For future reference a small red dot may be painted over this
particular "N" mark on the rotor to indicate the keyway up
reference position needed for proper timing.
If. in future timing checks, the red teeth appear in the distributor inspection windows and the "dotted "N"
does not show up in the "E" gap inspection hole, simply turn the magneto shaft 1-1/2 turns (or the
propeller 2 turns) in the direction of rotation and the magneto will be in the proper timing position.
Reissued: 9/23/80
POWER PLANT
2121