Adjusting The Carburetor - Stihl SR 200 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 (H) and low
speed screw (L) within fine limits.
Preparations
Shut off the engine.
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Check the air filter and clean or
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replace if necessary.
Check that the throttle cable is
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properly adjusted – readjust if
necessary – see chapter on
"Adjusting the Throttle Cable".
Check the spark arresting screen in
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the muffler and clean or replace if
necessary.
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Standard Setting
Turn high speed screw (H)
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counterclockwise as far as stop (no
more than 3/4 turn).
Turn the low speed screw (L)
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carefully clockwise as far as stop,
then turn it back 3/4 turn.
Adjusting Idle Speed
Carry out the standard setting.
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Start and warm up the engine.
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Engine stops while idling
Turn the idle speed screw (LA)
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clockwise until the engine runs
smoothly.
Erratic idling behavior, engine stops
even though setting of LA screw has
been corrected, poor acceleration
Idle setting is too lean
Turn the low speed screw (L)
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carefully counterclockwise, no
further than stop, until the engine
runs and accelerates smoothly.
Erratic idling behavior, engine speed
drops when swinging the machine
Idle setting is too rich
Turn the low speed screw (L)
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clockwise until the engine runs and
accelerates smoothly.
It is usually necessary to change the
setting of the idle speed screw (LA) after
every correction to the low speed
screw (L).
Fine tuning for operation at high altitude
A slight correction of the setting may be
necessary if engine does not run
satisfactorily:
Carry out the standard setting.
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Warm up the engine.
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Turn high speed screw (H) slightly
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clockwise (leaner) – no further than
stop.
NOTICE
After returning from high altitude, reset
the carburetor to the standard setting.
If the setting is too lean there is a risk of
engine damage due to insufficient
lubrication and overheating.
SR 200