IGNITION SYSTEM
6
12
Function
The ignition system is fully enclosed and has no moving
parts. It is insensitive to moisture and dirt. The design is
such that the ignition point does not need to readjustment.
Husqvarna K750 has integrated overspeed protection in the
electronic unit that limits the engine's speed to 9,300 rpm.
The ignition system consists of the primary coil (A) and
secondary coil (B) which are both surround ed by the iron
core (C). An electronic digital unit (D) manages the switch
function.
Current is generated in the primary coil when the fly -
wheel's permanent magnet passes the coil and has the voltage
sequence illustrated in the diagram below. (The dashed line
indicates the voltage that should be generated if the current
is not broken.)
The ignition point is determined by the electronic unit,
which sense the voltage variation in the primary coil and
breaks the current at the right level, at the same time the
engine piston is just below the upper turning point. At the
breaking instant the voltage in the primary coil rises from
5 V (volt) to approximately 200 V through induction. At the
same time a high voltage, approximately 20,000 volt, is
transformed in the secondary coil to the spark plug.
Electronic
circuit
breaker
STOP
control
Volts
+
-
0
Ignition
point
S
N
S
N
1
1
A
D
B
C
2
2
3
3
Ignition module
Individual components can not
be replaced.
The ignition lead, contact
unit to the spark plug and seals
on the ignition module can be
replaced.
The ignition module requires
no periodic servicing. Neverthe -
less, the distance to the flywheel's
magnet may need adjusting.
The short-circuit contact
(arrow) is connected to the stop
switch.
Ignition module
The ignition module's components are
fully enclosed to withstand external
manipulation. Individual components
can not be replaced.
The ignition lead, contact unit to the
spark plug and seals on the ignition
module can be replaced.
The ignition module requires no perio-
dic servicing. (Nevertheless, the distance
to the flywheel's magnet may need adjus-
ting.)
The ignition module has two connec-
tions. One to the spark plug and the
other is the short-circuit contact (arrow)
to the stop switch
Spark plug
The spark plug's electrode gap should be
.02 in./0.5 mm.
The electrodes should be free of soot
deposits and oil. Brush clean with a wire
brush.
A convex centre electrode and a worn
side electrode impair the ignition charac-
teristics. Replace the spark plug.
Spark plug
The electrode gap scale should
be .02 in./0.5 mm.
The electrodes should be free
of soot deposits and oil. Brush
clean with a wire brush.
Replace the spark plug if the
electrodes are worn.
0.5 mm
.02 in.
