Cessna 177 SERIES Service Manual page 170

3. Establish that the magneto is at the number
should break at the advanced firing position of num-
one firing position. It is possible for the timing
ber one cylinder. Loosen mounting nuts slightly and
mark to be visible while firing position is 180 degrees
rotate magneto case to cause the contacts to break at
from number one firing position. the correct position.
Tighten mounting nuts.
9. After tightening magneto mounting nuts, re-
NOTE
check timing. Make sure both magnetos are set to
fire at the same time.
Remove timing equipment,
It is necessary to "spark" the magneto to
install spark plugs and connect spark plug leads and
establish the correct firing position.
The ignition switch leads.
outlet plate with the spark plug leads must
be installed.
Hold number one spark plug
NOTE
lead (refer to figure 11-4) close to magneto
case. or ground the magneto and hold the
Beginning with the number one outlet, the
number one spark plug lead close to a good
magneto fires at each successive outlet in
ground. Rotate impulse coupling (left mag-
a counterclockwise direction, looking at
neto) or drive coupling (right magneto) in
the outlets. Connect number one magneto
normal direction of rotation until a spark
outlet to number one cylinder spark plug
occurs at this lead. (Impulse coupling
lead, number two outlet to the next cylin-
pawls must be depressed to turn magneto
der to fire, etc.
Engine firing order is
shaft in normal direction of rotation. )
listed in paragraph 11-12.
Turn coupling or drive coupling backwards
a few degrees, until timing mark is center-
b. BENDIX S-1200 SERIES.
The magneto must be
ed in ventilating plug hole and install timing
installed with its timing marks correctly aligned,
pin (or 0. 093 inch 6-penny nail) through hole
with number one cylinder on its compression stroke
in bottom of magneto next to flange and into
and with the number one piston at its advanced firing
mating hole in the rotor shaft. This locks
position. Refer to paragraph 11-12 for the advanced
the magneto approximately in firing posi-
firing position of number one piston.
To locate the
tion while installing on the engine.
compression stroke of number one cylinder, remove
the lower spark plug from number 2, 3 and 4 cylin-
4. If timing pin is not used, keep timing mark
ders. Place the thumb of one hand over the spark
centered in ventilating plug hole during magneto in-
plug hole of number one cylinder and rotate crank-
stallation.
shaft in the direction of normal rotation until the
5. Be sure magneto gasket (right magneto), mag-
compression stroke is indicated by positive pressure
neto adapter and gaskets (left magneto) are in place
inside the cylinder lifting the thumb off the spark plug
and that the engine is in the correct firing position,
hole.- After the compression stroke is attained, lo-
then install magneto approximately at the angle noted
cate number one piston at its advance firing position.
during removal. tighten mounting nuts finger tight.
Locating the advanced firing position of number one
piston may be obtained by rotating the crankshaft op-
NOTE
posite to its normal direction of rotation until the
piston is approximately 30 degrees before top dead
Remove timing pin (or nail) from magneto,
center (BTC) on the compression stroke of number
if installed.
Be sure to remove this pin
one cylinder. Then rotate crankshaft slowly in nor-
before rotating propeller.
mal direction of rotation to align the timing mark on
the FORWARD face of the starter ring gear with the
6. Connect a timing light to the capacitor (pri-
drilled hole in the forward end of the starter, making
mary lead) terminal at the rear of the magneto and
sure the final movement of the ring gear is in the
to a good ground.
direction of normal rotation.
7. Rotate propeller opposite to normal direction
of rotation a few degrees (approximately 5 degrees)
NOTE
to close magneto contact points.
An accurate top center indicator which
NOTE
screws into a spark plug mounting hole,
and a pendulum pointer mounted on a
Do not rotate propeller back far enough
360-degree timing disc may also be used
to engage impulse coupling, or propeller
to locate the advanced firing position.
will have to be rotated in normal direction
The timing disc should be adapted to fit
of rotation untii impulse coupling releases
over the end of the propeller spinner in
on the left magneto. then again backed-up
such a manner that it may be rotated as
to a few degrees before the firing position.
necessary.
In all cases, it must be
definitely determined that the number
8. Slowly advance propeller (tap forward with
one cylinder is at the correct firing po-
minute movements as firing position is approached)
sition and on the compression stroke,
in normal direction of rotation until timing light indi-
when the engine is turned in its normal
cates position at which contacts break.
The contacts
direction of rotation.
11-24 Change 2