Service Manual

2-1 IGNITION
Section 2
IGNITION
IGNITION SYSTEM
A transistor controlled ignition system is used for
FB46OV. This system consists of the following
components.
Ignition coil unit
Control unit (Igniter)
Permanent magnet flywheel
Spark plug
The ignition coil unit
is mounted outside the fly-
wheel on the cylinder block.
Since the transistor ignition system contains no
mechanical parts, no wear occurs and no periodic
maintenance
is required except for the spark plug.
Principle of Operation
: Primary coil
: Secondary coil
: Transistor
: Transistor
: Control Resister
F : Flywheel
CU
: Control Unit (Igniter)
SP
: Spark plug
: Control Resister SW : Stop switch
When voltage at point (A) is plus, base current
) flows into Transistor ). Then the
Transistor
is turned "ON" and allows
large amplified current to flow, during
which the Transistor does not operate
because Resister
( ) lowers valtage at point C.
As the flywheel continues to rotate, AC
power
is further generated in the primary coil
(L, ). Then the Transistor ) is turned
"ON" by high voltage
at point (C).
As soon as the Transistor ) is turned "ON",
the base current
) through Resistor (R, ) to
Transistor
) changes its flow to ) and to
Transistor thus the Transistor
) is
turned "OFF" because of voltage drop at point
(B).
This sudden current change induces high
voltage within the secondary coil
(L,), which
fires the spark plug.
SPARK CHECK
Remove spark plug and check spark by cranking
engine while having the plug touched against
engine block.
Keep
the plug as far away as
possible from the plug hole. To avoid an electric
shock do not hold the plug itself. Make sure to
hold the plug cap.
If there
is good spark between electrodes, the
ignition system
is in good condition.
If there
is no or very weak spark, clean spark
plug and regap to
0.6 to 0.7mm (0.024 to 0.028
in.). Replace spark plug if electrodes are worn.
See "Spark Plug Check and Cleaning" section.
FLYWHEEL REMOVAL
1. Remove spiral case. (Flywheel housing)
2. Disconnect spark plug cap from spark plug.
3. 'Carefully remove the wire out of spiral case.
CAUTION: Flywheel nut has a left-hand thread.
4. Place a pry bar against the thick root of the
blades to prevent the blades from breaking off.