Stihl 064 Service Manual page 86

STIHL 064, 066
Regulating low speed adjusting screw
Erratic idling behavior, poor
acceleration
- Idle setting too lean.
- Turn the low speed adjusting
screw counterclockwise until the
engine runs and accelerates
smoothly.
Exhaust smokes at idle speed
- Idle setting too rich.
- Turn the low speed adjusting
screw clockwise until the engine
speed drops.
- Turn screw back one quarter turn.
- Check that the engine accel-
erates smoothly when the throttle
is opened.
Note: A correction at the low
speed adjusting screw usually
necessitates a change in the
setting of the idle speed adjusting
screw.
11.7 Carburetor Adjustment
(Digital Ignition)
1 = High speed adjusting screw
2 = LED (066 only)
3 = Low speed adjusting screw
4 = Idle speed adjusting screw
Machines with digital ignition have
an electronic maximum speed gov-
ernor. Adjustment of the engine's
maximum speed is possible, but
not beyond the preset limit.
An excessively lean mixture does
not produce an increase in power -
it only increases the risk of engine
damage.
The light emitting diode (LED) aids
carburetor adjustment.
Standard setting
To adjust the carburetor without
a tachometer or if the LED fails,
carefully screw both adjusting
screws down onto their seats.
Then make the following adjustments:
High speed adjusting screw H:
back off 1 full turn
Low speed adjusting screw L:
back off 1 full turn
Note: This is the optimum setting of the
adjusting screws for normal operation at an
altitude of about 300 m (1,000 ft) above sea
level.
If the LED has failed and the adjustment
has to be made without a tachometer, do
not turn the high speed adjusting screw
beyond this standard setting, i.e. leaner.
Corrections to high speed adjusting
screw with tachometer (064)
If it is necessary to alter the setting of the
high speed adjusting screw, carry out the
adjustment as follows using an accurate
tachometer:
- Carefully screw the high speed adjusting
screw down onto its seat.
- From this position, back off the high
speed adjusting screw exactly two full
turns.
- Start the engine and allow it to warm up.
- Adjust idle speed correctly.
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