Air Filter; Adjusting The Carburetor - Stihl FS 120 Instruction Manual

18 Air filter

17.2 During Operation
After a long period of full throttle operation, allow
the engine to run for a short while at idle speed
so that engine heat can be dissipated by the flow
of cooling air. This protects engine-mounted
components (ignition, carburetor) from thermal
overload.
17.3 After Finishing Work
Storing for a short period: Wait for the engine to
cool down. Empty the fuel tank and keep the
machine in a dry place, well away from sources
of ignition, until you need it again. For longer out-
of-service periods – see "Storing the Machine".
18 Air filter
18.1 If there is a noticeable loss of
engine power
► Turn the choke knob to g.
1
► Loosen the screws (1).
3
2
► Remove the filter cover (2).
► Clean away loose dirt from around the filter (3)
and inside the filter cover.
► Remove and check the filter element – replace
it if is dirty or damaged.
► Fit the filter in the filter housing.
► Fit the filter cover.
0458-251-0121-B

19 Adjusting the Carburetor

19.1 General Information
The carburetor comes from the factory with a
standard setting.
This setting provides an optimum fuel-air mixture
under most operating conditions.
19.2 Preparations
► Shut off the engine.
► Mount the cutting attachment.
► Check the air filter and clean or replace if nec‐
essary.
► Check that the throttle cable is properly adjus‐
ted – readjust if necessary – see chapter on
"Adjusting the Throttle Cable".
19.3 Standard Setting
– High speed screw (H) = 3/4
– Low speed screw (L) = 3/4
► Turn high speed screw (H) counterclockwise
as far as stop (no more than 3/4 turn).
► Turn the low speed screw (L) clockwise as far
as stop, then turn it back 3/4 turn.
19.4 Adjusting Idle Speed
► Carry out standard setting.
► Start and warm up the engine.
19.4.1 Engine stops while idling
► Turn the idle speed screw (LA) clockwise until
the engine runs smoothly – the cutting attach‐
ment must not rotate.
English
H L
LA
L
31