Cleaning The Air Filter; Engine Management; Adjusting The Carburetor - Stihl BT 121 Instruction Manual

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Cleaning the Air Filter

If there is a noticeable loss of engine
power
1
3
2
N Turn the choke knob to g.
N Press in the tab (1) and remove the
filter cover (2).
N
Clean away loose dirt from around
the filter (3) and inside the filter
cover.
N Remove and check the filter
element – replace it if is dirty or
damaged.
N Install the filter element in the filter
cover.
N Refit the filter cover.
14

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

General Information
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
N Shut off the engine
N Remove the auger.
N Check the air filter and replace it if
necessary.
N Check that the throttle cable is
properly adjusted – readjust if
necessary – see chapter on
"Adjusting the Throttle Cable".
BT 121