Adjusting Breaker-Controlled Ignition; Magneto Edge Gap On Breaker-Controlled Ignition - Stihl 009 User Manual

STIHL 009, 010, 011
4.5.2 Adjusting Breaker-
Controlled Ignition
Resetting breaker point gap
In addition to the preparations
described under 4.5.1 (inserting the
dial gauge) it is necessary to remove
the flywheel in order to adjust ignition
timing.
Turn clutch in engine's normal
direction of rotation (clockwise) until
the dial gauge pointer remains
stationary (T D.C. position). Now set
dial gauge pointer to zero. Turn clutch
about a quarter of a revolution
clockwise and then backward again
until the dial gauge shows a reading
of 2.0 mm. Switch on the ignition
timing unit, slacken the contact set
and turn it until the indicator lamp on
the timing unit just lights up.
Then retighten the contact set
mounting screws and recheck ignition
timing. If it is now between 1.9 and 2.1
mm before T D.C., the breaker point
gap will be between 0.3 and 0.4 mm.
The breaker point gap, ignition timing
and magneto edge gap are interre-
lated. None of these values can be
altered without affecting the others.
However, this also means that if one
of these values is correctly set the
other two will normally be correct as
well. The dominating factor is the
magneto edge gap. If any variations
are experienced in practice,
preference should be given to
maintaining the correct edge gap.
Finish off by removing the test
equipment and reassembling the saw.
4.6 Magneto Edge Gap on
Breaker-Controlled Ignition
The position of the magnet at the
point of current interruption, i.e.
ignition, is called magnet breakdown
and is referred to in terms of the
magneto edge gap. The magneto
edge gap is, therefore, the distance
between the trailing edge of the north
pole shoe and the left-hand edge of
the center armature arm when the
contact breaker points begin to open.
This distance is 5 mm.
The magneto edge gap has a
decisive influence on the performance
of the ignition system. If it is too large,
the ignition voltage during starting will
be too low; however, if it is too small,
the engine will misfire at high speed.
If the ignition is properly timed the
magneto edge gap will automatically
be correct as the two factors are
interrelated. However, variations may
occur as a result of an accumulation
of maximum manufacturing
tolerances. The edge gap should,
therefore, also be checked whenever
the ignition timing is adjusted.
Preference should always be given to
maintaining the correct edge gap
even if this means that there are
minor discrepancies in ignition timing
and the breaker point gap.
To check the edge gap, first follow
procedure for checking ignition timing.
The magneto edge gap should then
be measured at the moment the
timing unit's indicator lamp lights up
(ignition point).
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