English
experience loss of performance and you
suspect a clogged screen, have your
muffler maintained by a STIHL servicing
dealer. Some state or federal laws or
regulations may require a properly
maintained spark arrestor for certain
uses. See the "Maintenance, Repair and
Storing" section of these Safety
Precautions. Remember that the risk of
a brush or forest fire is greater in hot or
dry conditions.
WARNING
Some STIHL power tools
are equipped with a cata-
lytic converter, which is
designed to reduce the
exhaust emissions of the
engine by a chemical
process in the muffler.
Due to this process, the
muffler does not cool
down as rapidly as con-
ventional mufflers when
the engine returns to idle
or is shut off. To reduce
the risk of fire and burn
injuries when using a cat-
alytic converter, always
set your power tool down
in the upright position and
never locate it where the
muffler is near dry brush,
grass, wood chips or
other combustible materi-
als while it is still hot.
Reactive Forces including Kickback
WARNING
Reactive forces may occur any time the
chain is rotating. Reactive forces can
cause serious personal injury.
12
The powerful force used to cut wood can
be reversed and work against the
operator. If the rotating chain is suddenly
and significantly slowed or stopped by
contact with any solid object such as a
log or branch or is pinched, the reactive
forces may occur instantly. These
reactive forces may result in loss of
control, which, in turn, may cause
serious or fatal injury. An understanding
of the causes of these reactive forces
may help you avoid the element of
surprise and loss of control. Sudden
surprise contributes to accidents.
The most common reactive forces are:
kickback,
–
pushback,
–
pull-in.
–
Kickback:
Kickback may occur
when the moving saw
chain in or near the upper
quadrant of the bar nose
is suddenly and signifi-
cantly slowed or stopped
as a result of contact with
an object or is pinched.
When this occurs, the energy driving the
chain can create a force that moves the
chain saw in a direction opposite to the
chain movement at the point where the
chain is slowed or stopped. This may
fling the bar up and back in a lightning
fast reaction mainly in the plane of the
bar and can cause severe or fatal injury
to the operator.
Kickback may occur, for example, when
the chain near the upper quadrant of the
bar nose contacts the wood or is
pinched during limbing or when it is
incorrectly used to begin a plunge or
boring cut.
The greater the force of the kickback
reaction, the more difficult it becomes for
the operator to control the saw. Many
factors influence the occurrence and
force of the kickback reaction. These
include chain speed, the speed at which
the bar and chain contact the object, the
angle of contact, the condition of the
chain and other factors.
MS 150 C