Piper COMANCHE PA-24-180 Service Manual page 383

PIPER COMANCHE SERVICE MANUAL
j.
Turn the crankshaft very slowly in direction of normal roation until the timing mark on the front
face of the ring gear align with the drilled hole in the starer or the timing mark on the back of the ring
gear aligns with the crankcase pating surfaces. At this point the light should go out
k. If the Light does not go out at this point. align ciming marks and rotate magneto on mounting
flange in the desred direction and repeat the procedure unil the light goes out a 25 degrees before top
dead center.
CAUTION
When timing retard breaker magnetos to the engine, only main breaker
points are timed. Never attempt to time retard breaker points to the
engine.
1. Tighten the two mountur
utr and replace the inspection plug.
m. After tghtening magneto nounung nuts, check trimng to make sure it is still correct.
n. Install the other magneto and time using the preceding instructions A through M.
o. With both magnetos timed to the engine and secured, check that they fire together. Rotate the
crankshaft opposie normal rotation to approximately 35 degrees BTC with No. I cylinder on the
compression stroke.
p. If the magnetos are tuned correctly, both timing lights will go out simultaneously when the
crankshaft is turned in the normal direction aligning the 25 degree marks with the drilled hole in the scater
housng or the crankcase parting surfaces.
q. Disconnect iinung light. Ascertain that the inpection plugs and breaker cover are installed and
secure.
r.
Install harness place and secure with screws.
s. Connect "P" leads and safety.
t.
Connect starring vibrator lead to the left -200 magnetos.
u. Secure engine cowling
7A-74 Starring Vibrator Checking Procedure.
a. Measure voltage between vibrator terminal marked "in" and the ground rerminal while operating
starter. Output must be at least 8-volts on 12-volt systems.
b
If voltage is adequate, listen for buzzing of vibraror during sarting If no buzzing is heard, either
the vibrator is defective or the circuit from the output "BO" terminal on the vibrator to the rerard (duai
breaker) magneto is open. Check both switch and retard circuits. Also check for good electrical ground.
c. Retard points may not be closing due to wrong adjustment, or may not be electricaly connected
in the circuit due to a poor connection. Inspect retard points to see if they close. Check for proper contact
at the switch and retard rerminals of rerard (dual breaker) magneto and at the vibrator. Check wiring.
d. Turn engine m proper direction of rotauon until retard points just open on No. one cylinder
position. Remove input connection from starter to prevent engine turning. Hold No. one plug head 5/16
inch from ground. energize vibrator by urnimng switch to start. Plug lead should throw a 5/16 inch spark
Observe spark at plugs spark cap. If spark is weak or missing, ry new vibrator. If this does not correct
trouble. remove magneto and check for improper internal tuning or improperly meshed distributor gears.
POWER PLANT
ISSUED: 8/18/72
2 E1