MS 251 C-Q
English
37
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
N Switch off the engine
N Check the air filter – clean or replace
it if necessary
N Turn the high speed adjusting
screw (H) counterclockwise as far
as possible (max. 3/4 turn)
N Turn the low speed adjusting
screw (L) clockwise until it is firmly
in its seat – then back off 1/4 turn
Setting the idle speed
N Make standard setting
N Start engine and let it warm up
Engine stops when idling
N Turn the idle speed adjusting screw
(LA) clockwise until the saw chain
begins to run – then turn it back
2 3/4 turn.
Saw chain rotates at idle speed
N Turn the idle speed screw (LA)
counterclockwise until the saw
chain stops turning – then turn
another 2 3/4 turns in the same
direction
WARNING
If the saw chain continues to keep
rotating in idle even after adjustment,
have the chain saw checked by a
servicing dealer.
Speed erratic when idling; poor
acceleration (despite standard setting of
low speed adjusting screw)
The idle setting is too lean.
N Carefully turn the low speed
adjusting screw (L)
counterclockwise until the engine
runs smoothly and accelerates
properly.
Whenever the low speed adjusting
screw (L) has been adjusted, it is usually
also necessary to readjust the idle
speed adjusting screw (LA).
Correcting the carburetor setting for use
at high altitudes
The setting may have to be marginally
corrected if engine performance is
unsatisfactory at high altitudes:
N Make standard setting
N Let the engine warm up
N Turn the high speed adjusting
screw (H) slightly clockwise (leaner)
– max. up to the stop
NOTICE
After descending from a high altitude,
restore the carburetor setting to the
standard setting.
If you make the setting too lean it will
increase the risk of engine damage
through lack of lubrication and
overheating.
Adjusting the Carburetor
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