6.
MAGNETO
6-
1
MAGNETO TROUBLESHOOTING
When engine does not
start
or
starts
with difficulty,
or
when its operation is unstable, the following
.tests will clarify if they are caused by a defect in magneto.
(1)
Check ignition cable for possible corrosion, broken, worn insulation or loose connection.
(2)
Check sparks as described in the following
-
section.
(3)
If
no spark flys, replace ignition coil.
..
6-2
SPARK
TESTING
Remove spark plug from cylinder head and place it on cylinder, with the ignition cable
connected to it.
Crank
the engine several times by recoil starter and observe sparks at the spark gap of spark
plug.
If
spark
is
strong, the ignition system .can be eliminated as the source
of
trouble.
If
the spark
is
weak
or
there is no spark. at all, repeat the checks. according to the trouble-
shooting chart "Ignition system problems caused by" (Refer to section
"
8
TROUBLE
-
SHOOTING").
BREAK-
IN
OPERATION
OF
REASSEMBLED ENGINE
overhauled engine must be operated carefully
to
break-in the parts.
ah
,
A
thorough break-in is indispensable particularly when the cylinder, piston
or
piston ring are
replaced with new ones.
.For
break-in of' overhauled engines; use mixture fuel
of
gasoline
20
:
1
part
oil for the first
ten
(1
0)
hours
of
operation.
8.
TROUBLESHOOTING
8-
1
TROUBLESHOOTING
The following three conditions must be fulfilled for satisfactory engine starting.
1.
The cylinder filled with a proper fuel- air mixture.
2.
Good compression in the cylinder.
3.
Good spark, properly timed, to ignite the mixture.
The engine cannot be started unless these three coditions are met. There are also other factors
which make engine start difficult, such as
a
heavy load initially applied
to
the engine, and
a high back pressure due
to
a long exhaust pipe.
The most common causes of engine troubles are given in
the
tables in the following pages.
..
.
-
27
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