(4) Hold the end of the cable about 1/16 of an inch away from the flywheel housing. If the cable is
unbroken, a spark will jump from the cable terminal to the flywheel housing. If a spark does not
jump, remove and replace the cable (29) and recheck. Should the spark not jump with the new
cable in place, the trouble is probably in the magneto. Use the above procedure to check all spark
plug cables.
c. Removal.
(1) Tag each cable so that it can be replaced in its proper position. Remove the holddown clamp
screws (27, fig. 20).
(2) Unscrew the four spark plug terminal connectors (30) and the four magneto terminal connectors
and remove the cables.
(3) Remove the holddown clamps from the cables.
d. Cleaning, Inspection, and Repair.
(1) Clean the cable shielding, connectors, and terminals with an approved cleaning solvent.
(2) Inspect the shielding for fraying or breaks. Replace all broken or frayed cables.
(3) Inspect the terminals and connectors for damage. Replace any damaged cables.
e. Reassembly and Installation.
(1) Replace the holddown clamps (28, fig. 20) on the cables.
(2) Insert the cable terminals (21, fig. 18) into the magneto and spark plug sockets (31, fig. 20) and
tighten the connectors (30, fig. 20).
(3) Position the holddown clamps over the screw holes and secure with screws (27) and lockwashers.
86. Spark Plugs
a. Removal.
(1) Unscrew the four connectors (30, fig. 20) holding the spark plug cables (29) to the spark plugs (31)
and remove the cables.
(2) Blow out the spark plug wells with compressed air.
(3) Remove the spark plugs with a spark plug wrench and lift out the plug gaskets.
(4) Plug the four spark plug holes with cork or wooden plugs, to prevent dirt from entering the
cylinders.
b. Cleaning and Inspection.
(1) Clean the outside of the spark plugs with an approved cleaning solvent.
(2) Inspect the terminal socket for corrosion. Clean with wire brush.
(3) Inspect the insulators for lead, carbon deposits, and cracks, clean all deposits from the insulators,
and use a brush to clean the threads. Replace any plugs with cracked insulators.
(4) Examine the spark plug electrodes for pitting. Replace a badly pitted spark plug.
(5) If the center electrodes are not excessively worn, file them level with a spark plug file.
(6) Adjust the spark plug gap to 0.030 ofan inch by bending the ground, or flat, electrode.
Caution: Do not bend the center electrode. To do so will break the insulation, rendering the spark
plug inoperative.
c. Installation.
(1) Remove the cork or wooden plugs from the spark plug holes in the cylinder head.
(2) Position the spark plug gasket over each spark plug, and install the plugs in the cylinder head.
(3) Use a spark plug socket and a torque wrench to tighten the spark plugs to a torque of from 25 to 30
foot-pounds.
(4) Insert the spark plug cable terminals (30, fig. 20) into the spark plug sockets (31) and secure the
connectors (30).
87. Magneto
a. Description. The engine magneto assembly provides the high voltage electrical current for the engine
ignition system. It is radio shielded
AGO 6871A
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