Tensioning The Chain; Checking Chain Tension; Fuel - Stihl MS 261 C-M Instruction Manual

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Tensioning the Chain

1
Retensioning during cutting work:
Shut off the engine.
N
Loosen the nuts.
N
Hold the bar nose up.
N
Use a screwdriver to turn the
N
tensioning screw (1) clockwise until
the chain fits snugly against the
underside of the bar.
While still holding the bar nose up,
N
tighten down the nuts firmly.
Go to "Checking Chain Tension".
N
A new chain has to be retensioned more
often than one that has been in use for
some time.
Check chain tension frequently –
N
see chapter on "Operating
Instructions".
20

Checking Chain Tension

Shut off the engine.
N
Wear work gloves to protect your
N
hands.
The chain must fit snugly against
N
the underside of the bar and it must
still be possible to pull the chain
along the bar by hand.
If necessary, retension the chain.
N
A new chain has to be retensioned more
often than one that has been in use for
some time.
Check chain tension frequently –
N
see chapter on "Operating
Instructions".

Fuel

This engine is certified to operate on
unleaded gasoline and with the mix ratio
50:1.
Your engine requires a mixture of high-
quality premium gasoline and high-
quality two-stroke air-cooled engine oil.
Use premium branded unleaded
gasoline with a minimum octane rating
of 89 (R+M)/2.
Note: Models equipped with a catalytic
converter require unleaded gasoline. A
few tankfuls of leaded gasoline can
reduce the efficiency of the catalytic
converter by more than 50%.
Fuel with a lower octane rating may
result in preignition (causing "pinging")
which is accompanied by an increase in
engine temperature. This, in turn,
increases the risk of the piston seizure
and damage to the engine.
The chemical composition of the fuel is
also important. Some fuel additives not
only detrimentally affect elastomers
(carburetor diaphragms, oil seals, fuel
lines etc.), but magnesium castings as
well. This could cause running problems
or even damage the engine. For this
reason it is essential that you use only
high-quality fuels!
Fuels with different percentages of
ethanol are being offered. Ethanol can
affect the running behaviour of the
engine and increase the risk of lean
seizure.
MS 261 C-M