g. When magneto is properly timed, the impulse
metal part of engine as shown in figure 4-4.
coupling will snap when the DC and X marked vane of the
flywheel lines up with mark on flywheel which should indicate
b. Turn engine over slowly using hand crank and watch
the centerline of number 1 and 3 cylinders. Check this by
for spark discharge which should occur during the cycle, at the
turning crankshaft over by hand. The impulse will also snap
instant the impulse coupling on the magneto snaps. Repeat
every 180 degrees of flywheel rotation thereafter.
this check with each ignition cable.
h. The proper spark advance is 23 degrees. Timing may
c. If there is a weak spark, or none at all, check magneto
be checked with a neon light, the running spark advance is
breaker point opening (paragraph 4-13). If this does not
indicated by a 1/8 inch hole on flywheel shroud, 23 degrees
remedy trouble it may be necessary to install a new condenser.
before vertical centerline of number 1 and 3 cylinders. Whiten
end of vane marked X with chalk or paint. The magneto
4-13. ADJUSTING ENGINE MAGNETO BREAKER POINTS.
rotates at crankshaft speed in clockwise direction as viewed
If ignition spark becomes weak after continued operation, the
from driving gear end of magneto. The magneto distributor
breaker points may have to be readjusted, resurfaced, or
rotor turns at half engine speed.
replaced, as follows:
CHECKING IGNITION SPARK.
If difficulty is
a. Remove magneto end cover and examine points. If
experienced in starting the engine or if engine misfires, the
there is evidence of pyramiding or pitting, resurface points
strength of the ignition spark may be tested as follows:
using a small tungsten file.
a. Disconnect number 1 ignition cable from spark plug
and hold terminal 1/8 inch away from air shroud or any other
Figure 4-3. Engine Ignition Timing