Piper Arrow IV Turbo Maintenance Manual page 622

2. The internal timing can be checked without a timing kit using the cast-in marks in the breaker
compartment. These marks indicate "E" gap and limits (refer to Figure 74-8). The point in the center of the
"E" gap boss indicates the exact "E" gap position. The width of the boss on either side of the point is the
allowable tolerance of ± 4°. In addition to these marks, the cam has an indented line across its end. When the
indented line is aligned with the mark at the top of the breaker housing, the rotating magnet is in its "E" gap
position. Check the timing using the following procedure:
A. Install the Rotor Holding Tool 11-8465 under the drive shaft nut and washer as shown in Figure
74-6.
The rotor holding tool facilitates the timing procedure. However,
it is possible to manually hold the shaft at the specified angle
when setting the breakers.
B. Turn rotating magnet in direction of rotation until painted chamfered tooth of distributor gear is
just becoming visible in timing window. Continue turning rotating magnet until line on end of cam
is aligned with mark at top of breaker housing. (Refer to Figure 74-8.) Tighten adjusting knob of
the holding tool to hold rotating magnet.
C. Fabricate a pointer as shown in Figure 74-9 and install the pointer under the cam screw so the
pointer indexes in the center of "E" gap position.
D. Connect the 11-9110 Timing Light or equivalent across breaker assembly. Adjust breaker contacts
to just open at this position.
E. Loosen holding tool and turn rotating magnet until cam follower is on high point of cam lobe.
Tighten holding tool and measure contact clearance. It must be 0.018 ± 0.006. If necessary,
readjust breaker. Check to be sure contacts open within "E" gap tolerance. Replace breaker
assembly if "E" gap tolerance and contact clearance cannot be obtained. Tighten breaker screws to
20 to 25 inch-pounds and recheck breaker settings.
MAGNETO INSTALLATION AND TIMING PROCEDURE. (Magneto To Engine) (Refer to Figure 74-
10.)
1. The timing marks are on the outer edge of the crankshaft counterweight blade between No. 2 and No.
4 cylinders. The inspection plug between No. 2 and No. 4 cylinders on the left top side of the crankcase must
be removed to view the marks on the crankshaft.
A. Plug one spark plug hole of the No.1 cylinder and place a thumb over the other plug hole. Have a
second person stand in front of the engine and turn the crankshaft in a counterclockwise direction
until pressure is felt on the thumb. No.1 piston is coming up on the compression stroke.
B. Remove the inspection hole plug and turn the crankshaft counterclockwise until the 20 degree
BTC mark appears in the center of the inspection hole. A timing device as described in Service
Bulletin M68-2, Rev. 1, may also be used.
C. Remove the inspection hole plug from the magneto. Turn the magneto coupling until the painted
chamfered tooth on the distributor gear is approximately centered in the inspection hole. Hold the
magneto in its approximate installed position. Note carefully the position of the coupling drive
lugs.
D. Lubricate the gear support shaft with clean lubricating oil and install the drive gear assembly so
the slots of the coupling bushings will be in the approximate position for aligning with the drive
coupling lugs on the magneto.
E. Insert the retainer into the gear hub slot. Apply a film of Lubriplate grease to each of the new
Effectivity
PA-28RT-201T
PIPER AIRCRAFT
PA-28RT-201 / 201T
MAINTENANCE MANUAL
—NOTE—
3D18
74-11-04
Page 74-09
December 1, 1978