plug gap In each cylinder. Magneto operation is timed to
the engine so that a spark occurs only when the piston is
on the proper stroke at a specified number of crankshaft
degrees before the top-dead-center piston position.
Maintenance of magnetos consists primarily of replacing
defective magnetos or components as explained in the
Prior to installation, perform internal
adjustments, breaker point dwell on master cam lobe, and
distributor alignment check.
Use reference marks on breaker
cam, distributor rotor, and magneto housing incorporated
on most assemblies to perform internal timing check.
Time high-tension Ignition system
magneto-to-engine, at a definite crankshaft position as
Position crankshaft to timing or
spark advance position using a piston position indicator
Align internal timing marks, and
slide magneto into place.
Shift magneto to retard position,
and turn magneto to advance until breaker points begin to
open as indicated by timing light.
cover, and leads.
Check timing of high-tension ignition
system magneto after a new magneto is Installed or if
incorrect timing is suspected, as follows.
position and check internal magneto timing marks.
Turn crankshaft one-fourth turn in
opposite direction of normal rotation.
coupling, rotate crankshaft in normal direction beyond
timing cylinder top-dead-center position; when impulse
coupling clicks, rotate crankshaft in opposite direction to
approximately 5 degrees advance of timing position.
ignition switches to ON position.
Apply even and equal torque to
each of cam retaining screws In direction opposite normal
rotation to remove gear train backlash.
While holding backlash out, turn
crankshaft until points begin to open as indicated by
If necessary, adjust magneto so
that timing light indicates points are beginning to open at
proper firing position.
Install and time low-tension Ignition
system magneto-to-engine, at a definite crankshaft
position, using the following procedures.
Depress magneto timing plunger
and turn magneto shaft until plunger engages fully In
notch of magneto shaft.
Position magneto In place while
If magneto does not line up with
centerline of engine, remove magneto, release plunger,
and turn magneto drive shaft 90 degrees. Repeat until
magneto lines up properly.
Hold plunger depressed and turn
magneto counterclockwise on its flange as far as
necessary to remove gear backlash.
Install magneto bolts securely in
Check timing of low-tension ignition
system magneto after a new magneto is installed or
incorrect timing is suspected.
Rotate engine one-fourth turn in
opposite direction of normal rotation and slide pointer of
piston position Indicator to top of scale.
Turn engine in direction of rotation
until slide pointer is starting to move down.