Adjusting The Carburetor - Stihl BR 350 Instruction Manual

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
To shut down the engine
N
Check the air filter and replace it if
N
necessary.
Check that the throttle cable is
N
properly adjusted – readjust if
necessary – see chapter on
"Adjusting the Throttle Cable".
Have the spark arresting screen
N
(not all markets) checked – see
"Inspection and Maintenance by
Dealer"
BR 350, BR 430
L
H
LA
BR 350
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 1/2 turns.
Start and warm up the engine.
N
BR 430
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 turn.
Start and warm up the engine.
N
Adjusting Idle Speed
Engine stops while idling
Check the standard setting.
N
Turn the idle speed screw (LA)
N
slowly 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) slowly
N
counterclockwise until the engine
runs and accelerates smoothly.
Erratic idling behavior
Idle setting is too rich
Turn the low speed screw (L)
N
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 in Mountains
or at Sea Level
A slight correction of the setting may be
necessary if engine power is not
satisfactory when operating at high
altitude or at sea level.
Check the standard setting.
N
Warm up the engine.
N
At high altitude
Turn high speed screw (H)
N
clockwise (leaner) – no further than
stop.
If the setting is too lean there is a risk of
engine damage due to insufficient
lubrication and overheating.
English
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