Piper Arrow IV, Maintenance Manual

Page: 639 / 752

REMOVAL OF MAGNETO.
Before removing the magneto, make sure magneto switches are off.
1. Remove the harness assembly terminal plate from the magneto.
—WARNING—
The magneto is not internally grounded; when the ground lead is
disconnected, the magneto is hot. Removing the harness assembly
terminal plate first and installing them last minimizes the danger
of starting the engine accidentally when the ground lead is
removed from the magneto.
2. Disconnect the ground lead at the magneto.
3. Remove the nuts and washers and draw the magneto from the engine.
TIMING PROCEDURE. (Internal Timing)
1. Remove the cover to the contact(s), distributor block, etc.
2. To internally time the contact assembly of the single-breaker magnetos, proceed as follows:
A. Loosen the nut securing the drive plate to the magneto shaft sufficiently in order to install the
Scintilla 11-8465 Rotor Holding Tool under the nut and flat washer as shown in Figure 74-24.
Tighten the nut securely.
B. Remove the timing inspection plug from the top of the magneto. Turn rotating magneto to proper
neutral position. This position is determined by locating keyways on drive end of magnet shaft at
12 o’clock with respect to nameplate on housing. Tighten adjusting knob of 11-8465 Rotor
Holding Tool until pressure is applied on housing flange preventing magnet from turning.
C. Loosen and rotate cam until cam follower of contact assembly rests on highest point of cam lobe.
Adjust contact assembly to obtain the clearance of 0.016 of an inch. Tighten contact assembly
securing screws to 20-25 inch-pounds.
D. Install the 11-8693 Timing Plate Assembly and the 11-8149 Pointer Assembly of the 11 - 8 1 5 0
Scintilla Timing Kit to breaker compartment of magneto. (Refer to Figure 74-25) Align pointer
assembly with the 0 mark on timing plate. Loosen adjusting knob of 11-8465 Rotor Holding Tool
and turn rotating magnet in normal direction of rotation until pointer indexes with the respective E
gap mark (15° ± 2° ). Tighten adjusting knob of 11-8465 Tool and remove the 11-8149 Pointer
Assembly from magneto. Using a timing light, adjust contact points to just open. This adjustment
shall be made by rotating cam, in opposite direction of rotation until contacts just open. While
holding cam in this exact position, push cam on magnet shaft as far as possible with the fingers.
Extreme care must be exercised in this operation. If cam adjustment is changed in the slightest
degree, the timing of the magneto will be thrown off. Do not drive cam on shaft with a mallet or
other instrument. Tighten the securing screw thereby drawing the cam down, evenly and tightly.
Torque screw to 16-20 inch-pounds. Loosen the 11-8465 Rotor Holding Tool adjusting knob and
return rotating magnet to neutral position. Reinstall the 11-8149 Pointer Assembly over 0 mark on
timing plate. Rotate magnet shaft in normal direction of rotation and check for opening of main
contact points at E gap setting (15° ± 2°).
3. If the distributor block was not removed from the housing, the internal timing may be checked by
turning the magneto in the normal rotation to number one firing position (keyway up and points just opening).
At this position, the reference line on the distributor block should line up between the L and LB marks on the
gear. On single contact magnetos the line should favor the L mark, if possible.
Effectivity 74-11-03
PA-28RT-201 Page 74-26
December 1, 1978
3E11
PIPER AIRCRAFT
PA-28RT-201 / 201T
MAINTENANCE MANUAL