Engine Management; Adjusting The Carburetor - Stihl MS 251 Instruction Manual

English
Thorough filter cleaning
Wash the filter in STIHL special-
N
purpose cleaner (special
accessory) or a clean, non-
flammable cleaning liquid (e. g.,
warm soapy water) – rinse the filter
from inside to out under a water jet
– do not use high-pressure cleaners
Dry all filter parts – do not expose to
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extreme heat
Do not oil the filter
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Reinstall filter
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Installing the air filter
1.
2.
Fit air filter
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Press the air filter in the direction of
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the filter housing and
simultaneously turn it clockwise
until the air filter engages – the
"STIHL" logo must be horizontal
Fit the shroud – see "Shroud"
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44

Engine Management

Exhaust emissions are controlled by the
design of the fundamental engine
parameters and components (e.g.
carburation, ignition, timing and valve or
port timing) without the addition of any
major hardware.

Adjusting the Carburetor

Basic information
The carburetor comes from the factory
with a standard setting.
The carburetor has been adjusted for
optimum performance and fuel
efficiency in all operating states.
Standard setting
Switch off the engine
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Check the air filter – clean or replace
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it if necessary
Turn the high speed adjusting
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screw (H) counterclockwise as far
as possible (max. 3/4 turn)
Turn the low speed adjusting
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screw (L) clockwise until it is firmly
in its seat – then back off 1/4 turn
Setting the idle speed
Make standard setting
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Start engine and let it warm up
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MS 251, MS 251 C