Adjusting - Stihl MS 270 User Manual

12.4

Adjusting

Standard setting
Do not remove the limiter cap to
carry out the standard setting.
– With this carburetor it is only
possible to correct the settings of
the high speed screw (H) and low
speed screw (L) within fine limits.
Make the following adjustments:
– Open the high speed screw (H)
counterclockwise as far as stop.
– Close the low speed screw (L)
clockwise as far as stop, then
open it one quarter turn counter-
clockwise.
Adjusting engine idle speed
Engine stops while idling
– Set the low speed screw (L) so it
is one quarter turn open.
– Turn the idle speed screw (LA)
clockwise until the saw chain
begins to move. Then turn it back
one full turn.
MS 270, MS 280
Chain runs while engine is idling
– Set the low speed screw (L) so it
is one quarter turn open.
– Turn the idle speed screw (LA)
counterclockwise until the chain
stops running. Then turn the
screw about another full turn in
the same direction.
Erratic idling behavior, poor
acceleration
although low speed screw is set one
quarter turn open.
– Idle setting too lean. Turn the low
speed screw (L) counter-
clockwise, but no further than
stop, 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).
Adjustments for operation at
high altitude or sea level
A minor correction may be
necessary if engine power is not
satisfactory when operating at high
altitude or at sea level.
– Check standard setting.
– Warm up the engine.
At high altitude
– Turn high speed screw (H)
clockwise (leaner) no further than
stop.
At sea level
– Turn high speed screw (H)
counterclockwise (richer) no
further than stop.
If the setting is made too lean there
is a risk of engine damage as a
result of insufficient lubrication and
overheating.
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