5. Ignition System - Stihl 064 Service Manual

STIHL 064, 066
IGNITION SYSTEM
5.
Warning! Exercise extreme caution when
carrying out maintenance and repair work
on the ignition system. The high voltages
which occur can cause serious or even
fatal accidents!
1 = Flywheel
2 = Ignition module
Older STIHL 064 saws are
equipped with a transistor-control-
led electronic (breakerless) magne-
to ignition system which requires
no outside power source (battery
or dynamo).
The system consists basically of
an ignition module and flywheel
and is easily accessible.
Note: A special flywheel is in-
stalled in models with heated
handles (with ring magnet for the
generator).
Analog ignition systems can be
converted to a digital system. This
necesitates changing the flywheel
and carburetor.
1 = Flywheel
2 = Wire for LED (066 only)
3 = Ignition module (digital)
Model 064 saws from machine
number X 18 761 250 are
equipped with an electronic digital
ignition which features a maximum
speed governor and requires no
outside power source.
The STIHL 066 is also equipped
with an electronic digital ignition
with a maximum speed governor.
The ignition module installed in the
066 has a second connection for a
light emitting diode (LED) which
aids carburetor adjustment.
In the digital ignition system the
zero values of the magnetic flux
in the magnetic field between the
flywheel and ignition module yoke
are evaluated to determine ignition
timing. This means that ignition
timing is tied to fixed physical
values and can be varied only by
the electronically stored advance
curve as a function of engine
speed.
CDIC and CDIC A digital ignition modules
feature an electronic cut-in threshold to
prevent backfiring during engine starts. An
ignition spark is generated only if the
cranking speed of the crankshaft is high
enough for its mass moment of inertia to
overcome combustion pressure.
Cut-in threshold:
CDIC ignition module (064) =
1,200 rpm
CDIC A ignition module (066) =
500 rpm
When using the spark test to
check installed digital ignition
modules with the sprark plug un-
screwed, make sure that the star-
ter rope is pulled at a sufficiently
high speed. If there is no spark at
the plug when the starter is pulled,
repeat the test at a higher cranking
speed.
45