Piper Navajo Chieftain PA-31-350 Service Manual page 483

NAVAJO CHIEFTAIN SERVICE MANUAL
c. The D2230 series magneto may be mounted to the engine without removing the cover from the
magneto. The cover also has switch terminal outlets for the right and left sides of the magneto, located in the
center of the harness lead outlet section of the cover. (Refer to Figure 8-15.)
NOTE
It is recommended that short adapter leads be fabricated to facilitate
connecting the timing light unit to the switch outlet terminals of the
cover. (Refer to Figure 8-15.)
d. The magnetos incorporate a built-in pointer and a degree wheel with sufficient reference to assist the
mechanic in magneto timing procedures. Printed upon the rotating magnet are marks to indicate magneto
neutral and magneto "E" gap (8°). (Refer to Figures 8-16 or 8-17.) Also included are retard angle references of
15, 20 and 25 degrees. These marks are set up for either clockwise (R) or counterclockwise (L) rotation of the
magneto as viewed from the magneto drive end. The timing tooth of each large distributor gear is marked with
red paint. (Refer to Figure 8-18.)
NOTE
A magneto, correctly timed internally, will have the timing teeth
of the large distributor gears approximately centered in the timing
windows at each end of the magneto; the R or L ("E" gap) mark
which is closest to the "K" or keyway up position indicator on the
rotor in alignment with the pointer, and both main breaker points
opening all at the same time. These three references, "E" gap,
painted teeth, and point opening are all used when timing the
magneto to the engine.
e. Remove the magneto drive gear backlash by turning the propeller opposite to normal rotation
approximately 40
°
past number one firing position; then turn propeller in direction of normal rotation up
to number one firing position of 20 BTC.
f. Remove the plug or adapter from the distributor inspection windows at either end of the magneto
housing. (Refer to Figure 8-18.) Also remove the plug from the "E" gap inspection window on the data plate
side of the magneto housing. (Refer to Figure 8-20.)
g. Turn the rotating magnet drive shaft in the normal direction of magneto rotation until the red
distributor tooth appears in the distributor inspection window, and also check to see if the letter "K"
appears in the "E" gap inspection window on the data plate side. If the letter "B" is in the window, turn
the magneto shaft 1-1/2 times in the direction of rotation and check again to be sure the "K" is in the
window on the data plate side and the red distributor tooth appears in each distributor inspection window.
On early model dual magnetos four "N" marks appear on the rotor at each neutral. The proper timing
position may be found on these magnetos by aligning the "N" mark in the "E" gap inspection window
which directly corresponds to the shaft keyway position. To determine this the magneto must be removed
from the engine and using a piece of safety wire or a paper clip with a short 90
°
bend on one end. Run the
hooked end of the wire around the magneto drive shaft at the rear of the drive coupling and find the
keyway slot. With this slot turned to the data plate side of the magneto housing, the "N" that appears in
the "E" gap inspection window is the proper mark for timing reference.
Reissued: 9/23/80
POWER PLANT
2120