Stihl 064 Service Manual page 85

STIHL 064, 066
11.6 Carburetor Adjustment
(Analog Ignition)
Adjusting screws on carburetor
1 = High speed adjusting screw
2 = Low speed adjusting screw
3 = Idle speed adjusting screw
When the engine is tested at the
factory the carburetor is set to
obtain a slightly richer mixture
to provide the cylinder bore and
bearings with additional lubricant
during the break-in period. This
setting should be left as it is for
the first three tank fillings. The
high speed adjusting screw may
then be turned up to 1/4 turn clock-
wise to obtain a leaner mixture.
Caution: The engine's maximum
permissible speed with bar and
chain must not be exceeded.
If the saw is used at high altitudes
(mountains) or near sea level, it
may be necessary to alter the car-
buretor setting slightly. This correc-
tion is made at the two adjusting
screws (H and L) as follows:
- Turn clockwise for a leaner mix-
ture (at high altitudes).
- Turn counterclockwise for a
richer mixture (at sea level).
Important: Note that even very
slight variations at the adjusting
screws produce a noticeable
change in engine running behavior.
Note: Always make sure that the
engine is warm and the air filter
clean before carrying out carbure-
tor adjustments.
Caution: The setting of the high
speed adjusting screw not only af-
fects the engine's performance but
also its maximum off-load speed.
If the setting is too lean (adjusting
screw turned too far clockwise),
the maximum permissible engine
speed will be exceeded. This can
result in damage to the engine
being caused by a lack of lubricant
and overheating.
Corrections to the high speed ad-
justing screw may only be carried
out if the maximum permissible en-
gine speed of 12,000 rpm (with bar
and properly tensioned chain) can
be checked with an accurate ta-
chometer.
Basic setting
If the carburetor has to be ad-
justed from scratch, carefully
screw both adjusting screws clock-
wise down onto their seats to ob-
tain a starting point for fine tuning.
Then make the following adjust-
ments:
High speed adjusting screw H:
back off 1 full turn
Low speed adjusting screw L:
back off 1 full turn
The saw must be run with the
basic carburetor setting (H = 1,
L = 1) if an accurate tachometer
is not available for checking the
engine's maximum speed.
Notes for adjustment of idle
speed
Engine stops while idling:
- Turn idle speed adjusting screw
clockwise until the chain begins
to run.
- Then turn it back one quarter turn.
Chain runs while engine is
idling
- Turn the idle speed adjusting
screw counterclockwise until the
chain stops running.
- Then turn it about another quar-
ter turn in the same direction.
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