Operating Instructions - Stihl MS 251 Manual De Instrucciones

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Operating Instructions

During the break-in period
A factory new machine should not be run
at high revs (full throttle off load) for the
first three tank fillings. This avoids
unnecessarily high loads during the
break-in period. As all moving parts
have to bed in during the break-in
period, the frictional resistances in the
shortblock are greater during this period.
The engine develops its maximum
power after about 5 to 15 tank fillings.
During work
NOTICE
Do not make the mixture leaner to
achieve an apparent increase in power –
this could damage the engine – see
"Adjusting the Carburetor".
NOTICE
Open the throttle only when the chain
brake is off. Running the engine at high
revs with the chain brake engaged
(chain locked) will quickly damage the
shortblock and chain drive (clutch, chain
brake).
Check chain tension frequently
A new saw chain must be retensioned
more frequently than one that has been
in use already for an extended period.
40
Chain cold
Tension is correct when the chain fits
snugly against the underside of the bar
but can still be pulled along the bar by
hand. Retension if necessary – see
"Tensioning the Saw Chain".
Chain at operating temperature
The chain stretches and begins to sag.
The drive links must not come out of the
bar groove on the underside of the bar –
the chain may otherwise jump off the
bar. Retension the chain – see
"Tensioning the Saw Chain".
NOTICE
The chain contracts as it cools down. If it
is not slackened off, it can damage the
crankshaft and bearings.
After a long period of full-throttle
operation
After a long period of full-throttle
operation, allow engine to run for a while
at idle speed so that the heat in the
engine can be dissipated by flow of
cooling air. This protects engine-
mounted components (ignition,
carburetor) from thermal overload.
After finishing work
Slacken off the chain if you have
N
retensioned it at operating
temperature during work.
NOTICE
Always slacken off the chain again after
finishing work. The chain contracts as it
cools down. If it is not slackened off, it
can damage the crankshaft and
bearings.
Short-term storage
Wait for engine to cool down. Keep the
machine with a full tank of fuel in a dry
place, well away from sources of
ignition, until you need it again.
Long-term storage
See "Storing the machine"
MS 251, MS 251 C