Piper COMANCHE PA-24-180 Service Manual page 322

PIPER COMANCHE SERVICE MANUAL
2A
I
FIGURE 7-15. ENGINE TIMING MARKS
744. Inollaion
And Timing Pocedure. (Timing Maneto m Enine.)
The magnetos can be insraled and
timed to the engine by the following procedure:
NOTE
Ascertain that the breakers are correct for proper internal tuming of
magnetos
a. Lift the engine cowling side panels.
b
Remove the top spark plug from No. one cylinder Place the thumb of one hand over the spark
plug hole and rotace the crankshafr in direction of normal rotation until the compression stroke is reached.
The compression stroke is indicated by a posiive pressure inside the cylinder tending to lift the thumb off
the spark plug hole. In this position both valves of No. one cylinder are closed. Turn the crankshair
opposite to its normal direction of rotation until it is approximatelv 35 degrees BTC on the compression
stroke of No. one cylinder. Rotate the crankshaft im its normal direcnton of rotation until the 25 degrees
mark on the back of the starter gear and the crankcase parting surface are algned. or the marks on the front
of the starer nng gear and the dnlled hole in the starter housing align. (Refer to Figure 7-15 )
NOTE
The impulse coupling magnero t-21) or the -200 shower of sparks
magneto can be used onlv on the left side of the engine as viewed from
the rear)
POWER PLANT
REVISED: 4/10/81
2 B12