Stihl MS 661 C-M

60 MS 661, MS 661 C-M
8. M-Tronic
For the sake of clarity, the
components in this chapter are
shown without filter cover, rewind
starter and the grommet on the
heater switch.
The M-Tronic basically consists of
the control unit (1), switch unit (2),
solenoid valve (3) diagnostic
socket (4), generator (5) and
flywheel (6).
The control unit (1) contains a high
energy ignition module and is
responsible for centralized control
of all engine functions. It adjusts
ignition timing and meters the exact
quantity of fuel as a function of
external conditions.
It is no longer necessary to carry out
a basic or standard carburetor
setting.
1166RA224 TG
6 15
2
4
3
The M-Tronic controls all operating
modes, such as start, idle, part and
full load, in response to external
conditions, e.g. operating at
different altitudes and temperatures
or with different fuel qualities – the
carburetor has no adjusting screws.
8.1 Calibrating the
Control Unit
The control unit has to be calibrated
if maximum engine speed is not
reached or the control unit and/or
carburetor or solenoid valve have
been replaced.
– Remove the saw chain and guide
bar and refit the chain sprocket
cover.
– Start the engine – do not blip the
throttle trigger – move Master
Control lever to start position }
Allow engine to run for at least
60 seconds in start position } and
then move the Master Control lever
to "STOP" without operating the
throttle trigger – that completes
calibration.
The control unit is adapted to the
carburetor during the run in the start
position }.
An immediate engine shutdown is
necessary for the information to be
saved to the control unit.