Engine Running Behavior; Storing The Machine; Checking And Replacing The Chain Sprocket - Stihl MS 171 Instruction Manual

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25.2 Checking the Spark Plug
► Clean dirty spark plug.
► Check electrode gap (A) and readjust if neces‐
sary – see "Specifications".
► Rectify the problems which have caused foul‐
ing of the spark plug.
Possible causes are:
– Too much oil in fuel mix.
– Dirty air filter.
– Unfavorable running conditions.
WARNING
Arcing may occur if the adapter nut (1) is loose
or missing. Working in an easily combustible or
explosive atmosphere may cause a fire or an
explosion. This can result result in serious inju‐
ries or damage to property.
► Use resistor type spark plugs with a properly
tightened adapter nut.
25.3 Installing the spark plug
► Install the spark plug and connect the spark
plug boot (press it down firmly) – reassembly
all other parts in the reverse sequence.

26 Engine Running Behavior

If engine running behavior is unsatisfactory even
though the air filter is clean and the carburetor is
properly adjusted, the cause may be the muffler.
Have the muffler checked for contamination (car‐
bonization) by your servicing dealer.
34
STIHL recommends that you have servicing and
repair work carried out exclusively by an author‐
ized STIHL servicing dealer.

27 Storing the Machine

For periods of about 30 days or longer
► Drain and clean the fuel tank in a well-ventila‐
ted area.
► Dispose of fuel properly in accordance with
local environmental requirements.
A
► If a manual fuel pump is fitted: Press the man‐
ual fuel pump at least 5 times.
► Start the engine and run it at idling speed until
it stops.
► Remove saw chain and guide bar; clean and
spray with protective oil
► Thoroughly clean the machine - pay special
attention to the cylinder fins and air filter
► When using biological chain oil (e.g. STIHL
BioPlus), fill the lubricant oil tank
► Store the machine in a dry and secure location
Keep out of the reach of children and other
unauthorized persons
28 Checking and Replacing
1
► Remove chain sprocket cover, saw chain and
guide bar.
► Release chain brake – pull hand guard against
the front handle
28.1
– after use of two saw chains or earlier
– if the wear marks (arrows) are deeper than
0.5 mm – otherwise the service life of the saw
chain is reduced – use check gauge (special
accessory) to test
Using two saw chains in alternation helps pre‐
serve the chain sprocket.
STIHL recommends use of original STIHL chain
sprockets in order to ensure optimal functioning
of the chain brake.
26 Engine Running Behavior
the Chain Sprocket
Fit new chain sprocket
0458-533-0121-E