Adjusting The Carburetor - Stihl KM 55 R Instruction Manual

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Adjusting the Carburetor

The carburetor comes from the factory
with a standard setting.
This setting provides an optimum fuel-air
mixture under most operating
conditions.
With this carburetor it is only possible to
adjust the high speed screw within fine
limits.
Standard Setting
Stopping the Engine
N
Mount the KombiTool complete with
N
working tool or cutting attachment.
Check the air filter and replace it if
N
necessary.
Have the spark arresting screen in
N
the muffler checked (not all
markets) – see "Inspection and
Maintenance by Dealer"
14
H L
LA
Turn high speed screw (H)
N
counterclockwise as far as stop (no
more than 3/4 turn).
Turn the low speed screw (L)
N
carefully clockwise as far as stop,
then turn it back 1.5 turns.
Start and warm up the engine.
N
Adjust idle speed with the idle speed
N
screw (LA) so that the cutting
attachment does not move.
Fine Tuning for Operation in Mountains
or at Sea Level
A slight correction of the setting of the
high speed screw (H) may be necessary
if engine power is not satisfactory when
operating at high altitude or at sea level.
Carry out the standard setting.
N
Warm up the engine for about
N
3 minutes at full throttle.
Rule of thumb:
Turn the high speed screw (H) about
one quarter of a turn for every 1000 m
(3300 ft) change in altitude.
At high altitude
Turn high speed screw (H)
N
clockwise (leaner) – no further than
stop.
At sea level
Turn high speed screw (H)
N
counterclockwise (richer) – no
further than stop.
It is possible that maximum engine
speed may be reached with the standard
setting in each case.
Aadjusting Idle Speed
It is usually necessary to change the
setting of the idle speed screw (LA) after
every correction to the low speed
screw (L).
Warm up the engine for about 3
N
minutes.
Engine stops while idling
Turn the idle speed screw (LA)
N
slowly clockwise until the engine
runs smoothly – the working tool or
cutting attachment must not move.
Cutting attachment runs when engine is
idling
Turn the idle speed screw (LA)
N
counterclockwise until the working
tool or cutting attachment stops
KM 55 R, KM 55 RC