4. Reverse the rotation approximately 25 degrees until the timing pin hole appears in the center of the vent
plug hole.
5. Hold the rotor by inserting the timing pin, and line the timing pin with the center of the vent plug holes and
install the magneto and gasket on the mounting pad of the accessory housing and remove the timing pin. Tighten
the nuts only finger tight.
—CAUTION—
The impulse coupling magneto can only be used on the left side of the
engine (as viewed from the rear).
b. Fasten the ground wire of an electric timing light to any unpainted metallic portion of the engine, and one
of the positive wires of the timing light to a suitable terminal connected to the ground terminal connection of the
left magneto. Turn the engine crankshaft several degrees from BTC in direction opposite to that of normal
rotation.
c. Turn on the switch of the timing light. Turn the crankshaft very slowly in the direction of normal rotation
until the timing mark on the front face of the starter ring gear aligns with the drilled hole in the starter housing, at
which point the light should come on, (on battery operated models). If not, turn the magneto in its mounting
flange slots and repeat the procedure until the light goes on at 25 degrees before top dead center. Tighten the two
mounting nuts and replace the bottom vent plug.
—NOTE—
AC timing lights operate in the reverse manner as described, the light
goes out when the breaker points open.
d. For the model 4050 magneto (without impulse coupling) "Spark-Out" the magneto by the following
method:
1. Install the gear and hold the number one lead wire 0.062 of an inch away from the magneto frame.
2. Turn the gear counterclockwise (left hand) vigorously through the flux lines until a strong spark occurs
at the number one lead.
3. Reverse the rotation until the timing pin hole appears. Insert the timing pin in the hole and install the
magneto and gasket on the right magneto mounting pad of the accessory housing. Remove the timing pin and
tighten the nuts finger tight only, proceed with the timing.
e. Connect the other positive wire of the timing light to a suitable terminal connection of the right magneto
and time the magneto in the same manner as described for the left magneto.
f. After both magnetos have been timed, leave the timing light wires connected and recheck the magneto
timing as previously described to make sure both magnetos are set to fire together. If timing is correct, both
timing lights will come on simultaneously when the 25 degree mark on the ring gear aligns with the drilled hole
in the starter housing. If the points open early, loosen the mounting nuts and rotate the magneto
counterclockwise. Secure the nuts and remove the timing lights.
8-25. OVERHAUL INSTRUCTIONS FOR MAGNETOS. (4200 series) The 4200 series magnetos must be
completely overhauled at every engine overhaul or when conditions indicate.
8-26. DISASSEMBLY OF MAGNETOS. (4200 series) (Refer to Figure 8-8.) Magneto disassembly is
accomplished in the following manner:
PIPER AIRCRAFT
PA-28-161 CADET
AIRPLANE MAINTENANCE MANUAL
Issued: FEBRUARY. 28, 1989
POWER PLANT
1J19
