STIHL FS 91, 91 R
WARNING
Read Instruction Manual thoroughly
before use and follow all safety
precautions – improper use can
cause serious or fatal injury.
ADVERTENCIA
Antes de usar la máquina lea y siga
todas las precauciones de
seguridad dadas en el manual de
instrucciones – el uso incorrecto
puede causar lesiones graves o
mortales.
Instruction Manual
Manual de instrucciones
Instruction Manual
1 - 57
Manual de instrucciones
58 - 119
Contents
English
Guide to Using this Manual 2
Safety Precautions and Working
Techniques 3
Approved Combinations of Cutting
Attachment, Deflector, Limit Stop,
Handle, Harness 19
Approved Power Tool Attachments 21
Mounting the Bike Handle 21
Mounting the Loop Handle 23
Original Instruction ManualPrinted on chlorine-free paper
Adjusting the Throttle Cable 24
Fitting the Carrying Ring 25
Mounting the deflector 25
Mounting the Cutting Attachment 26
Fuel 29
Fueling 31
Fitting the Harness 32
Balancing the Machine 33
Starting / Stopping the Engine 34
Transporting the Unit 37
Operating Instructions 38
Replacing the Air Filter 39
Engine Management 39
Printing inks contain vegetable oils, paper can be recycled.
Adjusting the Carburetor 39
Spark Arresting Screen in Muffler 40
Spark Plug 40
Engine Running Behavior 42
Lubricating the Gearbox 42
Storing the Machine 42
Sharpening Metal Cutting Blades 43
Maintaining the Mowing Head 43
Maintenance and Care 45
Main Parts 47
Specifications 50
Maintenance and Repairs 51
Disposal 52
Limited Warranty 52
STIHL Incorporated Federal
Emission Control Warranty
Statement 52
STIHL Incorporated California
Exhaust and Evaporative
Emissions Control Warranty
Statement 54
Trademarks 56
Allow only persons who fully understand
this manual to operate your trimmer /
brushcutter.
To receive maximum performance and
satisfaction from your STIHL trimmer /
brushcutter, it is important that you read,
understand and follow the safety
precautions and the operating and
maintenance instructions in chapter
"Safety Precautions and Working
Techniques" before using your trimmer /
brushcutter. For further information you
can go to www.stihlusa.com.
Contact your STIHL dealer or the STIHL
distributor for your area if you do not
understand any of the instructions in this
manual.
WARNING
Because a trimmer / brushcutter is a
high-speed cutting tool some special
safety precautions must be observed to
reduce the risk of personal injury.
Careless or improper use may cause
serious or even fatal injury.
Make sure your unit is equipped with the
proper deflector or limit stop, handle and
harness for the type of cutting
attachment being used. Always wear
proper eye protection.
© ANDREAS STIHL AG & Co. KG, 2022
0458-426-8621-A. VB0.B22.
0000007402_014_GB
FS 91, FS 91 R
This instruction manual is protected by copyright. All rights reserved, especially the rights to reproduce, translate and process
with electronic systems.
1
English
Guide to Using this Manual
Pictograms
The meanings of the pictograms
attached to or embossed on the
machine are explained in this manual.
Depending on the model concerned, the
following pictograms may be on your
machine.
Fuel tank for gasoline
and engine oil mixture
Press to operate decom
pression valve
Manual fuel pump
Press to operate manual
fuel pump
Filler hole for gear
lubricant
Air intake summer mode
Air intake winter mode
Handle heating
Symbols in Text
Many operating and safety instructions
are supported by illustrations.
The individual steps or procedures
described in the manual may be shown
in different ways:
N A bullet indicates a step or
procedure.
A description of a step or procedure that
refers directly to an illustration may
contain item numbers that appear in the
illustration. For example:
N Remove the screw (1)
N Pull the spark arresting screen (2)
-
upwards out of the muffler
In addition to the operating instructions,
this manual may contain paragraphs
that require your special attention. Such
paragraphs are indicated with the
symbols and signal words described
below:
DANGER
Indicates a hazardous situation that, if
not avoided, will result in death or
serious injury.
WARNING
Indicates a hazardous situation that, if
not avoided, could result in death or
serious injury.
NOTICE
Indicates a risk of property damage,
including damage to the machine or its
individual components.
Engineering Improvements
STIHL’s philosophy is to continually
improve all of its products. As a result,
engineering changes and improvements
are made from time to time. Therefore,
some changes, modifications and
improvements may not be covered in
this manual. If the operating
characteristics or the appearance of
your machine differs from those
described in this manual, please contact
your STIHL dealer or the STIHL
distributor for your area for assistance.
2
FS 91, FS 91 R
English
Safety Precautions and
Working Techniques
Because a trimmer /
brushcutter is a highspeed, fast-cutting power
tool sometimes equipped
with sharp cutting blades,
special safety precau
tions must be observed to
reduce the risk of per
sonal injury.
It is important that you
read, fully understand
and observe the following
safety precautions and
warnings. Read the
instruction manual and
the safety precautions
periodically. Careless or
improper use may cause
serious or fatal injury.
The terminology utilized in this manual
when referring to the power tool reflects
the fact that different types of cutting
attachments may be mounted on it. The
term "trimmer" is used to designate an
FS unit that is equipped with a nylon line
head or a head with flexible plastic
blades (i.e., the PolyCut head). A
"brushcutter" designates a unit
equipped with a rigid metal blade. Many
FS models may be used as either a
trimmer or a brushcutter – therefore, the
power tool is referred in this manual as a
"trimmer / brushcutter." Some smaller
and / or lightweight FS models may only
be used as a trimmer, i.e., they may not
be used with metal blades.
-
-
The term "clearing saw" indicates a
high-powered trimmer / brushcutter that
is particularly suited for use with a
circular saw blade to clear saplings or
small trees.
FS models with an "R" on the nameplate
were originally configured (at the time of
distribution) as a trimmer with a loop
handle.
WARNING
As more fully explained later in these
Safety Precautions, to reduce the risk of
personal injury, make sure your unit is
equipped with the proper handle,
harness and deflector or limit stop for the
type of cutting attachment you are using.
Use only cutting attachments that are
specifically authorized by STIHL for use
on your FS model.
Have your STIHL dealer show you how
to operate your power tool. Observe all
applicable local safety regulations,
standards and ordinances.
WARNING
Do not lend or rent your power tool
without the instruction manual. Be sure
that anyone using it understands the
information contained in this manual.
WARNING
The use of this machine may be
hazardous. If the rotating line or blade
comes in contact with your body, it will
cut you. When it comes in contact with
solid foreign objects such as rocks or
bits of metal, it may fling them directly or
by ricochet in the direction of bystanders
or the operator. Striking such objects
could damage the cutting attachment
and may cause blades to crack, chip or
break. Thrown objects, including broken
heads or blades, may result in serious or
fatal injury to the operator or bystanders.
STIHL does not recommend the use of
rigid blades when cutting in stony areas.
Use your trimmer / brushcutter equipped
with the appropriate cutting attachment
only for cutting grass, brush, wood and
similar material.
WARNING
Do not use it for other purposes, since
misuse may result in personal injury or
property damage, including damage to
the machine.
WARNING
Minors should never be allowed to use
this power tool. Bystanders, especially
children, and animals should not be
allowed in the area where it is in use.
WARNING
To reduce the risk of injury to bystanders
and damage to property, never let your
power tool run unattended. When it is
not in use (e.g. during a work break),
shut it off and make sure that
unauthorized persons do not use it.
Most of these safety precautions and
warnings apply to the use of all STIHL
trimmers / brushcutters. Different
models may have different parts and
controls. See the appropriate section of
your instruction manual for a description
of the controls and the function of the
parts of your model.
FS 91, FS 91 R
3
English
Safe use of a trimmer / brushcutter
involves
1. the operator
2. the power tool
3. the use of the power tool.
THE OPERATOR
Physical Condition
You must be in good physical condition
and mental health and not under the
influence of any substance (drugs,
alcohol, etc.) which might impair vision,
dexterity or judgment. Do not operate
this machine when you are fatigued.
WARNING
Be alert – if you get tired, take a break.
Tiredness may result in loss of control.
Working with any power tool can be
strenuous. If you have any condition that
might be aggravated by strenuous work,
check with your doctor before operating
this machine.
WARNING
Prolonged use of a power tool (or other
machines) exposing the operator to
vibrations may produce whitefinger
disease (Raynaud's phenomenon) or
carpal tunnel syndrome.
These conditions reduce the hand's
ability to feel and regulate temperature,
produce numbness and burning
sensations and may cause nerve and
circulation damage and tissue necrosis.
All factors which contribute to
whitefinger disease are not known, but
cold weather, smoking and diseases or
physical conditions that affect blood
vessels and blood transport, as well as
high vibration levels and long periods of
exposure to vibration are mentioned as
factors in the development of whitefinger
disease. In order to reduce the risk of
whitefinger disease and carpal tunnel
syndrome, please note the following:
– Most STIHL power tools are
available with an anti-vibration
("AV") system designed to reduce
the transmission of vibrations
created by the machine to the
operator's hands. An AV system is
recommended for those persons
using power tools on a regular or
sustained basis.
– Wear gloves and keep your hands
warm.
– Keep the AV system well
maintained. A power tool with loose
components or with damaged or
worn AV elements will tend to have
higher vibration levels.
– Maintain a firm grip at all times, but
do not squeeze the handles with
constant, excessive pressure. Take
frequent breaks.
All the above-mentioned precautions do
not guarantee that you will not sustain
whitefinger disease or carpal tunnel
syndrome. Therefore, continual and
regular users should closely monitor the
condition of their hands and fingers. If
any of the above symptoms appear,
seek medical advice immediately.
WARNING
The ignition system of the STIHL unit
produces an electromagnetic field of a
very low intensity. This field may
interfere with some pacemakers. To
reduce the risk of serious or fatal injury,
persons with a pacemaker should
consult their physician and the
pacemaker manufacturer before
operating this tool.
Proper Clothing
To reduce the risk of injury, the operator
should wear proper protective apparel.
WARNING
The deflector provided with your power
tool will not protect the operator from all
foreign objects (gravel, glass, wire, etc.)
thrown back by the rotating cutting
attachment. Thrown objects may also
ricochet and strike the operator.
4
FS 91, FS 91 R
English
WARNING
To reduce the risk of
injury to your eyes never
operate your power tool
unless wearing goggles
or properly fitted protec
tive glasses with
adequate top and side
protection complying with
ANSI Z87 "+" (or your
applicable national stand
ard). To reduce the risk of
injury to your face STIHL
recommends that you
also wear a face shield or
face screen over your
goggles or protective
glasses.
Wear an approved safety
hard hat to reduce the
risk of injury to your head
when there is a danger of
head injuries.
Power tool noise may
damage your hearing.
Wear sound barriers (ear
plugs or ear mufflers) to
protect your hearing.
Continual and regular
users should have their
hearing checked
regularly.
Be particularly alert and cautious when
wearing hearing protection because
your ability to hear warnings (shouts,
alarms, etc.) is restricted.
Always wear heavy duty
work gloves (e.g. made of
leather or other wear
resistant material) when
handling the machine
and metal blades. Heavy-
-
-
Avoid loose-fitting jackets, scarfs,
neckties, jewelry, flared or cuffed pants,
unconfined long hair or anything that
could become caught on branches,
brush or the moving parts of the unit.
Secure hair so it is above shoulder level.
THE POWER TOOL
For illustrations and definitions of the
power tool parts see the chapter on
"Main Parts."
duty, nonslip gloves
improve your grip and
help to protect your
hands.
Clothing must be sturdy
and snug-fitting, but allow
complete freedom of
movement. Wear long
pants made of heavy
material to help protect
your legs. Do not wear
shorts, sandals or go
barefoot.
Good footing is very
important. Wear sturdy
boots with nonslip soles.
Steel-toed safety boots
are recommended.
WARNING
Never modify this power tool in any way.
Only attachments supplied by STIHL
and expressly approved by STIHL for
use with the specific STIHL model are
authorized. Although certain
unauthorized attachments are useable
with STIHL power tools, their use may,
in fact, be extremely dangerous. For the
cutting attachments authorized by
STIHL for your unit, see the chapter
"Approved Combinations of Cutting
Attachment, Deflector, Limit Stop,
Handle and Harness" in the instruction
manual or the STIHL "Cutting
Attachments, Parts & Accessories"
catalog.
If this tool is subjected to unusually high
loads for which it was not designed (e.g.
heavy impact or a fall), always check
that it is in good condition before
continuing work. Check in particular that
the fuel system is tight (no leaks) and
that the controls and safety devices are
working properly. Do not continue
operating this machine if it is damaged.
In case of doubt, have it checked by your
STIHL servicing dealer.
THE USE OF THE POWER TOOL
Transporting the Power Tool
WARNING
To reduce the risk of injury from loss of
control and blade or line contact, never
carry or transport your power tool with
the cutting attachment moving.
FS 91, FS 91 R
5
English
389BA019 KN
It may be carried only in a horizontal
position. Grip the shaft in a manner that
the machine is balanced horizontally.
Keep the hot muffler away from your
body and the cutting attachment behind
you.
WARNING
Always shut off the engine and make
sure the cutting attachment has stopped
before putting a trimmer / brushcutter
down. When transporting it in a vehicle,
properly secure it to prevent turnover,
fuel spillage and damage to the unit.
STIHL recommends that you keep metal
blades covered with the transport guard
(optional accessory).
Fuel
Your STIHL power tool uses an oil-
gasoline mixture for fuel (see the "Fuel"
chapter in this instruction manual).
WARNING
Gasoline is an extremely
flammable fuel. If spilled
and ignited by a spark or
other ignition source, it
can cause fire and seri
-
ous burn injury or
property damage. Use
extreme caution when
handling gasoline or fuel
mix. Do not smoke or
bring any fire or flame
near the fuel or the power
tool. Note that combus
-
tible fuel vapor may
escape from the fuel
system.
Fueling Instructions
WARNING
To reduce the risk of fire and serious
personal injury, always place the power
tool on the ground before attempting to
fuel the machine.
WARNING
Pick a Safe Location
To reduce the risk of fire and explosion,
fuel your power tool in a well-ventillated
area, outdoors away from flames, pilot
lights, heaters, electric motors, and
other sources of ignition. Vapors can be
ignited by a spark or flame many feet
away. Select bare ground for fueling and
move at least 10 feet (3 m) from the
fueling spot before starting the engine.
Wipe off any spilled fuel before starting
your power tool. Take care not to get fuel
on your clothing. If this happens, change
your clothing immediately.
Allow the Power Tool to Cool Before
Removing the Fuel Cap
WARNING
Gasoline vapor pressure may build up
inside the fuel tank. The amount of
pressure depends on a number of
factors such as the fuel used, altitude
and temperature. To reduce the risk of
burns and other personal injury from
escaping gas, vapor and fumes, always
shut off the engine and allow it to cool
before removing the fuel cap.
The engine is air cooled. When it is shut
off, cooling air is no longer drawn across
the cylinder and engine temperatures
will rise for several minutes before
starting to cool. In hot environments,
cooling will take longer. To reduce the
risk of burns and other personal injury
from escaping gas, vapor and fumes,
allow the power tool to cool. If you need
to refuel before completing a job, turn off
the machine and allow the engine to cool
before opening the fuel tank.
Fuel Spraying or “Geysering”
WARNING
Removing the cap on a pressurized fuel
tank can result in gasoline, vapors and
fumes being forcefully sprayed out from
the fuel tank in all directions. The
escaping gasoline, vapors or fumes can
cause serious personal injury, including
fire and burn injury, or property damage.
6
FS 91, FS 91 R
English
Sometimes also referred to as "fuel
geysering," fuel spraying is an expulsion
of fuel, vapors and fumes which can
occur in hot conditions, or when the
engine is hot, and the tank is opened
without allowing the power tool to cool
adequately. It is more likely to occur
when the fuel tank is half full or more.
Pressure is caused by fuel and heat and
can occur even if the engine has not
been running. When gasoline in the fuel
tank is heated (by ambient
temperatures, heat from the engine, or
other sources), vapor pressure will
increase inside the fuel tank.
Some blends of gasoline, particularly
those designed for use in winter, are
more volatile and may cause tanks to
pressurize more quickly or create
greater pressure. At higher altitudes,
fuel tank pressurization is more likely.
How to Avoid Fuel Spraying
Removing the fuel cap on a pressurized
tank can result in gasoline, vapors and
fumes being forcefully sprayed out from
the fuel tank in all directions. To reduce
the risk of burns, serious injuries or
property damage from fuel spraying:
– Follow the fueling instructions in this
chapter.
– Always assume your fuel tank is
pressurized.
– Allow the power tool to cool before
removing the fuel cap.
– In hot environments, cooling will
take longer.
– The engine is air cooled. When it is
shut off, cooling air is no longer
drawn across the cylinder and the
engine temperature will rise for
several minutes before starting to
cool.
After the power tool has cooled
appropriately, follow the safety
instructions in this chapter for removing
the cap.
Never remove the fuel filler cap by
turning it directly to the open position.
First check for residual pressure in the
tank by slowly turning the cap
approximately 1/2 turn counterclockwise. The cap should be held in
place by the threads while allowing
residual vapor/pressure to be relieved.
Once the fumes or vapor have been
relieved, turn the cap further until it can
be removed from the tank opening.
Use only good quality fuel that is
appropriate for the season (summer v.
winter blends). Some blends of
gasoline, particularly winter blends, are
more volatile and can contribute to fuel
spraying.
Removing the Threaded Fuel Filler Cap
WARNING
After allowing the power tool to cool,
remove the fuel filler cap slowly and
carefully to allow any remaining
pressure build-up in the tank to release:
– While maintaining steady,
downward pressure, slowly turn the
cap approximately 1/2 turn counterclockwise.
– If any significant venting occurs,
immediately re-seal the tank by
turning the cap clockwise to the
closed position. Allow the power
tool to cool further before
attempting to open the tank.
– Turn the cap to the open position
only after the contents of the tank
are no longer under pressure.
– Never remove the cap by turning it
directly to the open position. First
allow the power tool to cool
adequately and then release any
residual pressure by slowly turning it
approximately 1/2 turn counterclockwise.
– Never attempt to remove the cap
while the engine is still hot or
running.
FS 91, FS 91 R
7
English
Installing the Threaded Fuel Filler Cap
WARNING
Unit vibrations can cause
an improperly tightened
fuel filler cap to loosen or
come off and spill quanti
ties of fuel. To reduce the
risk of fuel spillage and
fire, tighten the fuel filler
cap by hand with as
much force as possible.
Damaged or Broken Cap
If your fuel cap does not tighten properly,
it may be damaged or broken. Stop
using the power tool and take it to your
authorized STIHL dealer for repair.
Vapor Lock
WARNING
Vapor lock occurs when fuel in the fuel
line or carburetor vaporizes, causing
bubbles to block the free flow of liquid
fuel into the carburetor. Vapor lock
cannot be relieved or affected by
opening the fuel tank. Removing the fuel
filler cap without first allowing the power
tool to cool adequately can result in fuel
spraying. Always follow the instructions
in this section when removing the fuel
cap.
To relieve vapor lock:
– Press the manual fuel pump bulb at
least 20 to 30 times – even if the
bulb is already filled with fuel – to
clear the vapor and send liquid fuel
into the carburetor. Then start the
-
power tool. For specific starting
instructions, see the appropriate
section of your instruction manual.
– If the manual fuel pump bulb will not
be filled, place the Choke Knob to
the starting throttle position < and
pull the starter cord until the engine
runs.
– If your power tool will not restart, or
if vapor lock occurs again, the
power tool is being used in
conditions too extreme for the fuel
being used. Discontinue use and let
the engine cool completely before
attempting to start the power tool.
Before Operation
Take off the transport guard and inspect
the power tool for proper condition and
operation. (See the maintenance chart
near the end of the instruction manual.)
WARNING
Always check your power tool for proper
condition and operation before starting,
particularly the throttle trigger, throttle
trigger lockout, stop switch, cutting
attachment, deflector and harness. The
throttle trigger must move freely and
always spring back to the idle position.
Never attempt to modify the controls or
safety devices.
WARNING
Check fuel system for leaks, especially
the visible parts, e.g., filler cap, hose
connections, manual fuel pump (only for
power tools equipped with a manual fuel
pump). Do not start the engine if there
are leaks or damage – risk of fire. Have
the power tool repaired by a STIHL
servicing dealer before using it.
WARNING
Never operate your power tool if it is
damaged, improperly adjusted or
maintained, or not completely and
securely assembled.
WARNING
Check that the spark plug boot is
securely mounted on the spark plug – a
loose boot may cause arcing that could
ignite combustible fumes and cause a
fire.
WARNING
Do not mount any cutting attachment to
a unit without proper installation of all
required parts. Failure to use the proper
parts may cause the blade or head to fly
off and seriously injure the operator or
bystanders.
WARNING
The cutting attachment must be properly
tightened and not damaged. Inspect for
loose parts (nuts, screws, etc.) and for
cracked or damaged heads or cracked,
bent, warped or damaged blades.
8
FS 91, FS 91 R
English
A
000BA006 KN
B
000BA007 KN
Replace damaged heads or blades
before using the power tool. Always
keep blades sharp.
Keep the handles clean and dry at all
times; it is particularly important to keep
them free of moisture, pitch, oil, fuel mix,
grease or resin in order for you to
maintain a firm grip and properly control
your power tool.
WARNING
To reduce the risk
of personal injury
to the operator
from blade or line
contact and
thrown objects,
make sure your
unit is equipped
with the proper
deflector or limit
stop, handle and
harness for the
type of cutting
attachment being
used (see chart in
the chapter on
"Approved Combi
nations of Cutting
Attachment,
Deflector, Limit
Stop, Handle and
Harness".)
As can be seen in that chart, some
cutting attachments may require you to
change your deflector, limit stop, handle
and / or harness.
Keep the deflector (and the attached
skirt where appropriate) adjusted
properly at all times (see chapters on
"Mounting the Deflector" and "Mounting
the Cutting Attachment" of your
instruction manual.)
Arrows on the deflector (A) and limit
stop (B) (as seen from the underside)
show the correct direction of rotation of
the cutting attachment. When viewed
from above, however, the cutting
attachment rotates counterclockwise.
-
Adjust carrying harness and hand grip to
suit your size before starting work. The
machine should be properly balanced as
specified in your instruction manual for
proper control and less fatigue in
operation. To be better prepared in case
of an emergency, practice releasing the
unit from the harness as quickly as
possible.
For specific starting instructions, see the
appropriate section of your instruction
manual.
Starting
Start the engine at least 10 feet (3 m)
from the fueling spot, outdoors only.
For specific starting instructions, see the
appropriate section of your manual.
Place the power tool on firm ground or
other solid surface in an open area.
Maintain good balance and secure
footing.
WARNING
To reduce the risk of injury from blade or
line contact, be absolutely sure that the
cutting attachment is clear of you and all
other obstructions and objects, including
the ground, because when the engine
starts at starting-throttle, engine speed
will be fast enough for the clutch to
engage and move the cutting
attachment.
Once the engine has started,
immediately blip the throttle trigger,
which should release the starting throttle
and allow the engine to slow down to
idle.
With the engine running only at idle,
attach the power tool to the spring hook
of your harness (see appropriate
chapter of this manual).
WARNING
Your power tool is a one-person
machine. Do not allow other persons in
the general work area, even when
starting.
WARNING
To reduce the risk of injury from loss of
control, do not attempt to "drop start"
your power tool.
FS 91, FS 91 R
9
English
002BA055 KN
002BA054 KN
WARNING
When you pull the starter grip, do not
wrap the starter rope around your hand.
Do not let the grip snap back, but guide
the starter rope to rewind it properly.
Failure to follow this procedure may
result in injury to your hand or fingers
and may damage the starter
mechanism.
Important Adjustments
WARNING
To reduce the risk of personal injury
from loss of control or contact with the
running cutting attachment, do not use
your unit with incorrect idle adjustment.
At correct idle speed, the cutting
attachment should not move. For
directions on how to adjust idle speed,
see the appropriate section of your
instruction manual.
If you cannot set the correct idle speed,
have your STIHL dealer check your
power tool and make proper
adjustments and repairs.
During Operation
Holding and Controlling the Power Tool
Always hold the unit firmly with both
hands on the handles while you are
working.
Wrap your fingers and thumbs around
the handles, keeping the handles
cradled between your thumb and
forefinger. Keep your hands in this
position to have your power tool under
control at all times. Make sure your
trimmer handles and grips are in good
condition and free of moisture, pitch, oil,
fuel mix or grease.
Make sure you always have good
balance and secure footing.
Models with bike handle
Right hand on control handle, left hand
on left handle.
Models with loop handle
Left hand on loop handle, right hand on
control handle, even if you are lefthanded.
WARNING
Never attempt to operate
your power tool with one
hand. Loss of control of
the power tool resulting in
serious or fatal injury may
result. To reduce the risk
of cut injuries, keep
hands and feet away
from the cutting attach
-
ment. Never touch a
moving cutting attach
-
ment with your hand or
any other part of your
body.
WARNING
Do not overreach. Keep proper footing
and balance at all times. Special care
must be taken in slippery conditions (wet
ground, snow) and in difficult, overgrown
terrain. Watch for hidden obstacles such
as tree stumps, roots and ditches to
avoid stumbling. For better footing, clear
away scrub and cuttings. Be extremely
cautious when working on slopes or
uneven ground.
WARNING
To reduce the risk of injury from loss of
control, never work on a ladder or on any
other insecure support. Never hold the
cutting attachment above waist height.
Working Conditions
Operate and start your power tool only
outdoors in a well ventilated area.
Operate it under good visibility and
daylight conditions only. Work carefully.
10
FS 91, FS 91 R
English
15m (50ft)
WARNING
As soon as the engine is
running, this product gen
erates toxic exhaust
fumes containing chemi
-
cals, such as unburned
hydrocarbons (including
benzene) and carbon
monoxide, that are
known to cause respira
-
tory problems, cancer,
birth defects, or other
reproductive harm. Some
of the gases (e.g. carbon
monoxide) may be color
less and odorless. To
reduce the risk of serious
or fatal injury / illness
from inhaling toxic fumes,
never run the machine
indoors or in poorly venti
lated locations.
WARNING
If the vegetation being cut or the
surrounding ground is coated with a
chemical substance (such as an active
pesticide or herbicide), read and follow
the instructions and warnings that
accompanied the substance at issue.
WARNING
Inhalation of certain dusts, especially
organic dusts such as mold or pollen,
can cause susceptible persons to have
an allergic or asthmatic reaction.
Substantial or repeated inhalation of
dust and other airborne contaminants, in
particular those with a smaller particle
size, may cause respiratory or other
illnesses. Control dust at the source
FS 91, FS 91 R
where possible. Use good work
practices, such as operating the unit so
that the wind or operating process
directs any dust raised by the power tool
-
away from the operator. Follow the
recommendations of EPA / OSHA /
NIOSH and occupational and trade
associations with respect to dust
("particulate matter"). When the
inhalation of dust cannot be
substantially controlled, i.e., kept at or
near the ambient (background) level, the
operator and any bystanders should
wear a respirator approved by NIOSH /
MSHA for the type of dust encountered.
-
Operating Instructions
WARNING
Do not operate your power tool using the
starting throttle lock, as you do not have
-
control of the engine speed.
In the event of an emergency, shut off
the engine immediately by pressing the
stop switch.
WARNING
The cutting attachment
continues to rotate for a
short period after the
throttle trigger is released
(flywheel effect.)
WARNING
The rotating cutting attachment may
fling foreign objects directly or by
ricochet a great distance.
To reduce the risk of eye and other injury
always wear proper eye protection (see
the chapter on "Proper Clothing") and
ensure that bystanders are at least
50 feet (15 m) away. To reduce the risk
of damage to property, also maintain this
distance from such objects as vehicles
or windows. Even maintaining a
minimum distance of 15 meters cannot
exclude the potential danger. Any
coworkers who must be in the restricted
area should also wear goggles or
protective glasses. Stop the engine
immediately if you are approached.
WARNING
Inspect the work area: To
reduce the risk of injury,
remove stones, pieces of
metal and other solid
objects which could be
thrown 15 meters or more
by the cutting attachment
or damage the cutting
attachment and property
(e.g. parked vehicles,
windows).
WARNING
This trimmer / brushcutter is normally to
be used at ground level with the cutting
attachment parallel to the ground. Use of
a trimmer / brushcutter above ground
level or with the cutting attachment
perpendicular to the ground may
11
English
increase the risk of injury, since the
cutting attachment is more fully exposed
and the power tool may be more difficult
to control. Never use your trimmer /
brushcutter as a hedge trimmer.
WARNING
During cutting, check the tightness and
the condition of the cutting attachment at
regular short intervals with the engine
and attachment stopped. If the behavior
of the attachment changes during use,
stop the engine immediately, wait until
the cutting attachment stops, and check
the nut securing the attachment for
tightness and the blade or head for
cracks, wear and damage.
WARNING
A loose blade or head may vibrate,
crack, break or come off the trimmer /
brushcutter, which may result in serious
or fatal injury. Make sure that the cutting
attachment is properly tightened. Use
the wrench supplied or one of sufficient
length to obtain the proper torque. If the
blade or head loosens after being
properly tightened, stop work
immediately. The retaining nut may be
worn or damaged and should be
replaced. If the blade or head continues
to loosen, see your STIHL dealer. Never
use a trimmer / brushcutter with a loose
cutting attachment.
WARNING
Replace a cracked, damaged or wornout head or a cracked, bent, warped,
damaged, dull or worn out blade
immediately, even if damage is limited to
superficial cracks. Such attachments
may shatter at high speed and cause
serious or fatal injury.
WARNING
Some STIHL mowing heads have a
metal core. High-speed contact with
rock or other hard objects may create
sparks, which can ignite flammable
materials under certain circumstances.
Flammable materials include dry
vegetation and brush, particularly when
weather conditions are hot and dry.
When there is a risk of fire or wildfire, do
not use a mowing head with a metal core
around dry vegetation or brush. Contact
your local fire authorities or the U.S.
Forest Service if you have any question
about whether vegetation and weather
conditions are suitable for the use of a
mowing head with a metal core. STIHL
does not recommend using a mowing
head with a metal core when cutting in
rocky areas or in areas with debris or
other objects that could create sparks.
WARNING
When using rigid blades, avoid cutting
close to fences, sides of buildings, tree
trunks, stones or other such objects that
could cause the power tool to kick out or
could cause damage to the blade.
STIHL recommends use of the nylon line
heads for such jobs. In addition, be alert
to an increased possibility of ricochets in
such situations.
WARNING
If a rotating metal blade strikes a rock or
other hard object, sparks may be
created, which can ignite flammable
materials under certain circumstances.
Flammable materials can include dry
vegetation and brush, particularly when
weather conditions are hot and dry.
When there is a risk of fire or wildfire, do
not use metal blades around flammable
materials or around dry vegetation or
brush. Contact your local fire authorities
or the U.S. Forestry Service if you have
any question about whether vegetation
and weather conditions are suitable for
the use of a metal blade.
WARNING
If the head, blade or deflector becomes
clogged or stuck, always shut off the
engine and make sure the cutting
attachment has stopped before
cleaning. Grass, weeds, etc. should be
cleaned off the blade or from around the
head at regular intervals.
WARNING
To reduce the risk of unintentional
rotation of the cutting attachment and
injury, always shut off the engine and
remove the spark plug boot before
replacing the cutting attachment. To
reduce the risk of injury, always shut off
the engine before adjusting the length of
the nylon line on manually adjustable
mowing heads.
WARNING
The gearbox becomes hot during
operation. To reduce the risk of burn
injury, do not touch the gear housing
when it is hot.
12
FS 91, FS 91 R
English
WARNING
Never modify your muffler. Any
modification could cause an increase in
heat radiation, sparks or sound level,
thereby increasing the risk of fire, burn
injury or hearing loss. You may also
permanently damage the engine. Have
your muffler serviced and repaired by
your STIHL servicing dealer only.
WARNING
The muffler and other parts of the engine
(e.g. fins of the cylinder, spark plug)
become hot during operation and remain
hot for a while after stopping the engine.
To reduce risk of burns, do not touch the
muffler and other parts while they are
hot. Keep the area around the muffler
clean. Remove excess lubricant and all
debris such as pine needles, branches
or leaves. Let the engine cool down
sitting on concrete, metal, bare ground
or solid wood (away from any
combustible substances.
WARNING
An improperly mounted or damaged
cylinder housing or a
damaged/deformed muffler shell may
interfere with the cooling process of the
muffler. To reduce the risk of fire or burn
injury, do not continue work with a
damaged or improperly mounted
cylinder housing or a
damaged/deformed muffler shell.
Your muffler is furnished with a spark
arresting screen designed to reduce the
risk of fire from the emission of hot
particles. Never operate your unit with a
missing or damaged spark arresting
screen. If your gas/oil mix ratio is correct
(i.e., not too rich), this screen will
normally stay clean as a result of the
heat from the muffler and need no
service or maintenance. If you
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 pro
cess in the muffler. Due
to this process, the muf
-
fler does not cool down
as rapidly as conven
-
tional mufflers when the
engine returns to idle or
is shut off. To reduce the
risk of fire and burn inju
-
ries when using a
catalytic 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 com
bustible materials while it
is still hot.
USING THE CUTTING ATTACHMENT
For an illustration of the various cutting
attachments and instructions on proper
mounting see the chapter on "Mounting
the Cutting Attachment" in your
instruction manual.
WARNING
To reduce the risk of severe or fatal
injury from blade contact and / or loss of
control, never attempt to use a metal
blade on an FS model for which it is not
authorized.
Using the Mowing Heads
Do not use with mowing line longer than
the intended length. With a properly
-
mounted deflector, the built-in linelimiting blade will automatically adjust
the line to its proper length.
-
Using the unit with an overly long nylon
cutting line increases the load on the
engine and reduces its operating speed.
This causes the clutch to slip
continuously and results in overheating
and damage to important components
(e.g. clutch, polymer housing
components). Such damage could,
among other things, cause the cutting
attachment to rotate at idle.
-
FS 91, FS 91 R
13
English
002BA354 KN
002BA177 KN
Mowing heads are to be used only on
trimmers / brushcutters equipped with a
line-limiting blade in the deflector in
order to keep the line at the proper
length (see "Main Parts" chapter in your
instruction manual).
If the lawn edges are planted with trees
or bordered by a fence etc., it is best to
use a nylon line head. It achieves a
"softer" cut with less risk of damaging
tree bark etc. than polymer blades.
However, the polymer-bladed STIHL
PolyCut produces a better cut if there
are no plants along the edge of the lawn.
Sharpening is not necessary, and worn
polymer blades are easily replaced.
WARNING
To reduce the risk of serious injury,
never use wire or metal-reinforced line
or other material in place of the nylon
cutting lines. Pieces of wire could break
off and be thrown at high speed toward
the operator or bystanders.
STIHL SuperCut mowing head
Fresh line is advanced automatically.
Frayed line is replaced by a simple
adjustment (see instruction sheet
supplied with mowing head).
STIHL AutoCut mowing head
Nylon cutting line advances
automatically when tapped against the
ground (TapAction).
STIHL TrimCut mowing head
Frayed line is replaced by a simple
adjustment (see instruction sheet
supplied with mowing head).
STIHL PolyCut mowing head
Uses either nylon lines or nonrigid,
pivoting polymer blades.
Observe wear indicators.
WARNING
Three rectangular wear limit marks are
applied to the base (periphery) of the
PolyCut. To reduce the risk of serious
injury from breakage of the head or
blades, the PolyCut must not be used
when it has worn as far as one of these
marks. It is important to follow the
maintenance instructions supplied with
the head.
STIHL FixCut mowing head
Uses pre-cut lengths of nylon line.
Observe wear indicators.
Do not continue using the mowing head
if the raised moldings (1) on the base
are missing or worn – see right
illustration above. The mowing head
may otherwise shatter and flying objects
could result in injury to the operator or
bystanders. Install a new mowing head.
14
FS 91, FS 91 R
English
002BA135 KN
002BA355 KN
0000-GXX-0499-A0
Risk of Kickout (Blade Thrust) with all
Rigid Cutting Blades
WARNING
Kickout (blade thrust) is
the sudden and uncon
-
trolled motion towards
the operator's right or
rear that can occur when
the shaded area (espe
-
cially the darkly shaded
area) of a rotating blade
comes in contact with a
solid rigid object like a
tree, rock, bush or wall.
The rapid counterclock
-
wise rotation of the blade
may be stopped or
slowed, and the cutting
attachment may be
thrown to the right or to
the rear.
This kickout (blade thrust) may cause
loss of control of the power tool and may
result in serious or fatal injury to the
operator or bystanders. To reduce the
risk of injury, extreme caution should be
used when cutting with the shaded area
of any rigid blade.
Using the Grass Cutting Blade
All kinds of grass and weeds can be
easily cut with the grass cutting blade.
The power tool is swept in an arc similar
to a scythe.
WARNING
To reduce the risk of serious or fatal
injury from blade breakage, never
attempt to use this blade to cut woody
materials.
The 4-tooth grass cutting blade is
intended to cut grass and weeds. It has
4 cutting knives with cutting edges on
both sides, i.e. front and rear. When the
cutting edges on one side become dull,
the blade can be turned over to utilize
the cutting edges on the other side.
The 8-tooth grass cutting blade is
recommended for cutting fern or reed.
Both types of grass cutting blade have to
be resharpened when all cutting edges
are dull.
Using the Brush Knife
When fitted to the power tool, the brush
knife is suitable for applications ranging
from cutting matted grass to clearing
weeds, wild growth and scrub.
To cut wild growth and scrub, lower the
rotating brush knife down onto the
growth to achieve a chopping effect –
but keep the tool below waist height at
all times.
WARNING
Exercise extreme caution when using
this method of cutting. The higher the
cutting attachment is off the ground, the
greater the risk of loss of control and of
cuttings being thrown sideways.
Use the power tool like a scythe to cut
grass, i.e. sweep it to and fro in an arc.
WARNING
When cutting woody materials, use the
left side of the blade to avoid "kickout"
(blade thrust) situations.
WARNING
Improper use of a brush knife may cause
it to crack, chip or shatter. Thrown blade
fragments may seriously or fatally injure
the operator or bystanders. To reduce
the risk of injury, avoid contact with hard
or solid foreign objects such as stones,
rocks or pieces of metal.
FS 91, FS 91 R
15
English
000BA016 KN
WARNING
When cutting young saplings or other
woody materials up to 2 cm (3/4 in.) in
diameter, use the left side of the blade to
avoid "kickout" situations (see section
on "Risk of kickout (blade thrust) with all
rigid cutting blades"). Do not attempt to
cut woody material with a larger
diameter, since the blade may catch or
jerk the power tool forward. This may
cause damage to the blade or power tool
or loss of control of the power tool,
resulting in personal injury. Use a
circular saw blade for such work.
WARNING
Inspect the brush knife at regular short
intervals for signs of damage. Do not
continue working with a damaged brush
knife. Resharpen the brush knife
regularly (when it has dulled noticeably).
Using the Circular Saw Blade
Circular saw blades are suitable for
thinning brush and cutting small trees up
to a diameter of 4 cm (1 1/2 in.). Do not
attempt to cut trees with larger
diameters, since the blade may catch or
jerk the trimmer / brushcutter forward.
This may cause damage to the blade or
loss of control of the power tool and
result in serious injury. Use a chain saw
for such work.
replaced by the special limit stop
deflector (see chapter on "Mounting the
Deflector"). This limit stop helps to keep
the unit positioned against the tree
during the cutting process.
Inexperienced users should place the
left side of the stop against the tree trunk
before beginning to cut. This will keep
the trimmer / brushcutter against the tree
during the cutting operation and will
reduce the risk of loss of control and
possible kickout (described above and
briefly again below).
002BA214 ST
Before starting the cut, accelerate the
engine up to full throttle. Perform cut
with uniform pressure. STIHL
recommends that the circular saw blade
be applied to the right of the tree, using
the non-shaded area of the blade, as
shown in the illustration above.
16
WARNING
To reduce the risk that the blade will
crack and / or break, avoid all contact
with stones, rocks or the ground.
Sharpen blades in a timely manner as
specified – dull teeth may cause the
blade to crack or shatter.
When a trimmer / brushcutter with a
circular saw blade is used to cut down
small trees, STIHL recommends that the
standard deflector be removed and
FS 91, FS 91 R
English
002BA068 KN
WARNING
The risk of kickout is highest when
cutting in the darker shaded area. To
reduce the risk of kickout and resulting
injury, do not use this area of the circular
saw blade for cutting trees or shrubs.
Special techniques using the lighter
shaded areas of the blade to cut shrubs
and trees should only be used by
experienced operators with specialized
training in the use and control of the
trimmer / brushcutter.
WARNING
To reduce the risk of loss of control and
serious injury to the operator or
bystanders by a kickout, never use a
circular saw blade on a trimmer /
brushcutter with a loop handle, but
rather only on one with a bicycle handle.
When felling small trees, maintain a
distance of at least two tree lengths from
the nearest coworker.
WARNING
In order to reduce the risk of injury from
thrown objects or operator contact with
the blade or head, be sure to remount
the standard deflector when no longer
using a circular saw blade.
MAINTENANCE, REPAIR AND
STORING
Maintenance, replacement, or repair of
the emission control devices and
systems may be performed by any
nonroad engine repair establishment or
individual. However, if you make a
warranty claim for a component which
has not been serviced or maintained
properly, STIHL may deny coverage.
WARNING
Use only identical STIHL replacement
parts for maintenance and repair. Use of
non-STIHL parts may cause serious or
fatal injury.
Strictly follow the maintenance and
repair instructions in the appropriate
sections of your instruction manual.
WARNING
Always stop the engine and make sure
that the cutting attachment is stopped
before doing any maintenance or repair
work or cleaning the power tool. Do not
attempt any maintenance or repair work
not described in your instruction manual.
Have such work performed by your
STIHL servicing dealer only.
Wear gloves when handling or
performing maintenance on blades.
WARNING
Use the specified spark plug, and make
sure it and the ignition lead are always
clean and in good condition. Always
press the spark plug boot snugly onto
the spark plug terminal of the proper
size. (Note: If the terminal has a
detachable SAE adapter nut, it must be
securely attached.) A loose connection
between the spark plug and the ignition
wire connector in the boot may create
arcing that could ignite combustible
fumes and cause a fire.
WARNING
Never test the ignition system with the
spark plug boot removed from the spark
plug or with a removed spark plug, since
uncontained sparking may cause a fire.
WARNING
Do not operate your power tool if the
muffler is damaged, missing or modified.
An improperly maintained muffler will
increase the risk of fire and hearing loss.
Your muffler is equipped with a sparkarresting screen to reduce the risk of
fire; never operate your power tool if the
screen is missing, damaged or clogged.
Remember that the risk of a brush or
forest fire is greater in hot or dry
weather.
In California, it is a violation of § 4442 or
§ 4443 of the Public Resources Code to
use or operate gasoline-powered tools
on forest-covered, brush-covered or
grass-covered land unless the engine’s
exhaust system is equipped with a
complying spark arrester that is
maintained in effective working order.
The owner/operator of this product is
responsible for properly maintaining the
spark arrester. Other states or
governmental entities/agencies, such as
the U.S. Forest Service, may have
similar requirements. Contact your local
fire agency or forest service for the laws
or regulations relating to fire protection
requirements.
FS 91, FS 91 R
17
English
WARNING
Never repair damaged cutting
attachments by welding, straightening or
modifying the shape. This may cause
parts of the cutting attachment to come
off and result in serious or fatal injuries.
Keep blades sharp. Tighten all nuts,
bolts and screws, except the carburetor
adjustment screws, after each use.
Do not clean your machine with a
pressure washer. The solid jet of water
may damage parts of the machine.
Store the power tool in a dry and high or
locked location out of reach of children.
Before storing for longer than a few
days, always empty the fuel tank. See
chapter "Storing the Machine" in the
instruction manual.
18
FS 91, FS 91 R
Approved Combinations of Cutting Attachment, Deflector, Limit Stop, Handle, Harness
10
1
2
3
4
5
7
12
13
14
15
22
26
28
16
23
24
25
23
24
25
25
27
27
28
28
29
9
21
20
19
18
17
6
0000080004_003
11
8
Cutting Attachment Deflector, Limit Stop Handle Harness
English
FS 91, FS 91 R
19
English
Approved Combinations
The complete combination includes:
– Cutting attachment
– Deflector or limit stop
– Handle
– Harness
Select correct combination from the
table according to the cutting
attachment you intend to use.
WARNING
To reduce the risk of injury, only the
cutting attachments, deflectors or limit
stops, handles and harnesses shown in
each row of the table may be used
together. No other combinations are
permitted.
Cutting Attachments
Mowing heads
1 STIHL SuperCut 20-2
2 STIHL AutoCut C 25-2
3 STIHL AutoCut C 26-2
4 STIHL AutoCut 25-2 / AutoCut 27-2
5 STIHL AutoCut 36-2
6 STIHL FixCut 31-2
7 STIHL TrimCut 31-2
8 STIHL TrimCut 32-2
9 STIHL DuroCut 20-2
10 STIHL PolyCut 20-3
11 STIHL PolyCut 28-2
Metal cutting attachments
12 Grass cutting blade 230-4
(230 mm dia.)
13 Grass cutting blade 230-8
(230 mm dia.)
14 Brush knife 250-3
(250 mm dia.)
15 Scratcher tooth circular saw blade
200
(200 mm dia.)
16 Chisel tooth circular saw blade 200-
22 (4112), chisel tooth circular saw
blade 200-22 HP (4001)
WARNING
Non-metal grass cutting blades, brush
knives and circular saw blades are not
approved.
Deflectors, Limit Stop
17 Deflector for mowing heads
18 Deflector with
19 skirt and blade, for mowing heads
20 Deflector without skirt and blade, for
metal cutting attachments 10 to 12
21 Limit stop for circular saw blades
Handles
22 Loop handle
23 Loop handle with
24 barrier bar
25 Bike handle
Harnesses
26 Shoulder strap may be used
27 Shoulder strap must be used
28 Full harness may be used
29 Full harness must be used
WARNING
Based on the cutting attachment being
used:
Choose the proper deflector in order to
reduce the risk of serious personal injury
from thrown objects and contact with the
cutting attachment.
Make sure your unit is equipped with the
proper handle and harness in order to
reduce the risk of serious personal injury
from loss of control and contact with the
cutting attachment.
To reduce the risk of serious personal
injury from contact with the cutting
attachment, use grass cutting metal
blades and brush knives on this unit only
if equipped with a bike handle or a loop
handle with barrier bar. Use circular saw
blades on this unit only if equipped with
a bike handle.
Do not use rigid polymer blades on this
unit.
20
FS 91, FS 91 R
English
1
7
A
250BA046 KN
Approved Power Tool
Attachments
The following STIHL attachments may
be mounted to the basic power tool:
Attachment
BF Cultivator
1) 2)
FCS
FH 145° Power scythe
1)
HL 0°
HL 145°
HT
RG
KB (4601)
1)
1)
3)
1)
KW (4601)
1)
not approved for bike-handled
machines
2)
shoulder strap not necessary
3)
use barrier bar on loop-handled
machines
Application
Edger
Long reach hedge
trimmer
Long reach hedge
trimmer
Pole pruner
Weeder
Bristle brush
1)
PowerSweep
Mounting the Bike Handle
Mounting Bike Handle with Swiveling
Handle Support
The machine is supplied with the
swiveling handle support already
mounted on the shaft. To mount the
handlebar it is necessary to remove the
clamp moldings.
Removing the Clamp Moldings
N Pull out the wing screw – the
washer (6) remains on the wing
screw.
N Separate the clamp moldings – the
springs (4 and 5) remain in the
lower clamp.
Securing the Handlebar
N Place the handlebar (7) in the lower
clamp (1) so that distance A is no
more than 15 cm (6 in).
N Place the upper clamp in position
and hold both clamp moldings
together.
N Push the wing screw through the
two clamps as far as stop – hold all
parts together and secure them.
FS 91, FS 91 R
N Hold the lower clamp (1) and upper
clamp (2) firmly together.
N Release the wing screw (3) – the
clamps are loose once the wing
screw has been released. They are
pushed apart by the two
springs (4 and 5).
21
English
13
9
11
12
7
13
0000-GXX-0511-A0
10
Mounting the Control Handle
15
14
8
N Place the secured assembly on the
handle support (8) with the wing
screw at the side nearest the
engine.
N Push the wing screw into the handle
support as far as stop and then
screw it down – but do not finally
tighten yet.
N Line up the handlebar at a right
angle to the drive tube – check
distance A again.
N Tighten down the wing screw firmly.
0000-GXX-0510-A0
N Take out the screw (9) – the nut (10)
remains in the control handle (11).
N Push the control handle onto the
handlebar (7) until the holes (13)
line up – the throttle trigger (12)
must point towards the gearbox.
N Insert the screw (9) and tighten it
down firmly.
Fitting the Throttle Cable
NOTICE
Do not kink the throttle cable or lay it in
tight radii – make sure the throttle trigger
moves freely.
14
15
15
0000-GXX-0512-A1
N Position the clamp (15) and handle
support (14) against the drive tube.
N Close the throttle cable
retainer (15). The retainer (15)
snaps into place.
Adjusting the Throttle Cable
N Check adjustment of throttle cable –
see chapter on "Adjusting the
Throttle Cable".
22
FS 91, FS 91 R
English
2
002BA098 KN
1
1
5
4
002BA099 KN
2
3
6
7
Swiveling the Handlebar
Transport position
90°
3
7
N Loosen the wing screw (3) and
unscrew it until the handlebar (7)
can be rotated.
N Rotate the handlebar 90°
counterclockwise and then swing
the handles down.
N Tighten down the wing screw (3)
firmly.
Working position
N Reverse the sequence described
above to swing the handles up and
turn the handlebar clockwise.
Mounting the Loop Handle
Mounting Loop Handle with Barrier Bar
0000-GXX-0513-A1
N Fit the square nuts (1) in the barrier
bar (2); the holes must line up.
N Place the clamp (3) in the loop
handle (4) and position them both
against the drive tube (5).
N Position the clamp (6) against the
drive tube.
N Place the barrier bar (2) in position
as shown.
N Line up the holes.
N Insert the screws (7) in the holes
and screw them into the barrier
bar (2) as far as stop.
N Go to "Securing the Loop Handle".
FS 91, FS 91 R
23
English
7
8
5
4
1
6
1
3
8
7
002BA614 KN
9
4
A
002BA615 KN
002BA655 KN
Mounting the Loop Handle without
Barrier Bar
N Place the clamp (3) in the loop
handle (4) and position them both
against the drive tube (5).
N Position the clamp (6) against the
drive tube.
N Line up the holes.
N Fit washers (8) on the screws (7)
and insert the screws in the holes.
Fit the square nuts (1) and screw
them down as far as stop.
N Go to "Securing the Loop Handle".
Securing the Loop Handle
The loop handle can be adjusted to suit
the height and reach of the operator and
the application by changing
distance (A).
Recommendation: distance (A):
about 20 cm (8 in)
N Slide the handle to the required
position.
N Line up the loop handle (4).
N Tighten down the screws until the
loop handle can no longer be
rotated on the drive tube. If no
barrier bar is fitted – lock the nuts if
necessary.
The sleeve (9) (not fitted on all models)
must be between the loop handle and
the control handle.
Adjusting the Throttle Cable
It may be necessary to correct the
adjustment of the throttle cable after
assembling the machine or after a
prolonged period of operation.
Adjust the throttle cable only when the
unit is completely and properly
assembled.
N Set the throttle trigger to the full
throttle position.
N Carefully rotate the screw in the
throttle trigger in the direction of the
arrow until you feel initial resistance.
Then rotate it another half turn in the
same direction.
24
FS 91, FS 91 R
English
1
002BA529 KN
002BA636 KN
2
1
3
3
002BA637 KN
1.
2.
002BA646 KN
Fitting the Carrying Ring
Polymer Version
For position of carrying ring see "Main
Parts".
N Push the carrying ring (1) over the
drive tube.
N Insert the M5 nut in the hex recess
N Fit the M5x14 screw.
N Line up the carrying ring.
N Tighten down the screw firmly.
in the carrying ring.
Mounting the deflector
Mounting the Deflector
1 Deflector for mowing attachments
2 Deflector for mowing heads
Deflectors (1 and 2) are both mounted to
the gearbox in the same way.
N Place the deflector on the gearbox
flange.
N Insert the screws (3) and tighten
them down firmly.
Fitting the Skirt and Blade
WARNING
Risk of injury from thrown objects and
contact with the cutting attachment.
These parts must be fitted to the
deflector (1) when you use a mowing
head.
Fitting the Skirt
N Slide the lower guide slot of the skirt
onto the deflector – it must snap into
position.
Removing the Skirt
FS 91, FS 91 R
N Insert the stop pin into the hole in
the skirt and use it to push the skirt
to the left.
N Pull the skirt off the deflector.
25
English
002BA638 KN
7
002BA639 KN
6
002BA104 KN
2
002BA266 KN
Mounting the Blade
N Slide the line limiting blade into the
guide on the skirt.
N Insert the screw and tighten it down
firmly.
Mounting the Limit Stop
WARNING
Risk of injury from thrown objects and
contact with the cutting attachment.
Always fit the limit stop (6) when you use
a circular saw blade.
N Position the limit stop (6) on the
gearbox flange.
N Insert the screws (7) and tighten
them down firmly.
Mounting the Cutting
Attachment
Placing power tool on the ground
N Shut off the engine.
N Lay your power tool on its back so
that the cutting attachment
mounting face is pointing up.
Mounting Hardware for Cutting
Attachments
The mounting hardware supplied
depends on the cutting attachment that
comes as original equipment with the
new machine.
Machine supplied with mounting
hardware
Mowing heads and metal cutting
attachments may be mounted.
3
2
1
0000-GXX0500-A0
Depending on the cutting attachment, it
may be necessary to use the nut (3) and
rider plate (2). The thrust plate (1) must
be used with all cutting attachments.
These parts are included in a kit
supplied with the machine and are also
available as special accessories.
Machine supplied without mounting
hardware
Only mowing heads may be used which
mount directly to the shaft (2).
26
FS 91, FS 91 R
English
6
7
2
002BA330 KN
6
0000-GXX-1323-A0
4
1
2
3
5
6
1
0000-GXX-1324-A0
2
3
4
Blocking the Shaft
The output shaft (2) must be blocked
with the stop pin (6) or screwdriver (6) to
mount or remove cutting attachments.
These parts come standard with the
machine or are available as special
accessories.
N Insert the stop pin (6) or
screwdriver (6) in the hole (7) in the
gearbox as far as stop – and apply
slight pressure.
N Rotate shaft, nut or cutting
attachment until the stop pin slips
into position and blocks the shaft.
Removing the Mounting Hardware
N Block the shaft (5) with the stop pin
(1).
N Use the combination wrench (2) to
loosen and remove the nut (3)
clockwise (left-hand thread).
N Take the rider plate (4) off the
shaft (5). Do not remove the thrust
plate (6).
Mounting the Cutting Attachment
WARNING
Risk of injury from thrown objects and
contact with the cutting attachment. Use
a deflector that matches the cutting
attachment – see "Mounting the
Deflector".
Fitting Mowing Head with Screw
Mounting
Keep the instruction leaflet for the
mowing head in a safe place.
N Fit the thrust plate (1).
N Screw the mowing head (3)
counterclockwise on to the shaft (4)
as far as stop.
N Block the shaft (4) with the stop pin
(2).
N Tighten down the mowing head (3)
firmly.
NOTICE
Remove the tool used to block the shaft.
FS 91, FS 91 R
27
English
Remove the mowing head.
N Block the shaft (4) with the stop pin
(2).
N Unscrew and remove the mowing
head (3) clockwise.
Fitting Mowing Head without Screw
Mounting
Keep the instruction leaflet for the
mowing head in a safe place.
STIHL FixCut 31-2
N Push the thrust washer (3) (convex
side up) over the shaft (1) until it is
seated on the base.
N Block the shaft.
N Use the combination wrench (5) to
screw the mounting nut (4) onto the
output shaft and it tighten down
firmly.
WARNING
If the mounting nut has become too
loose, fit a new one.
NOTICE
Remove the tool used to block the shaft.
Removing the Mowing Head
N Block the shaft.
N Use the combination wrench to
loosen and unscrew the mounting
nut counterclockwise from the
output shaft.
Mounting Metal Cutting Attachments
Keep the leaflet and packaging of the
metal cutting attachment in a safe place.
Mount the cutting attachment the right
way round
Cutting attachments with 3 or 4 teeth (1,
3) may point in either direction – these
cutting attachments must be turned over
regularly to help avoid one-sided wear.
The cutting edges of cutting
attachments 2, 4 and 5 must point
clockwise.
Direction of rotation is indicated by an
arrow on the inside of the deflector.
N Fit the thrust plate (2).
N Place the mowing head on the
thrust plate (2).
WARNING
Collar (see arrows) must engage the
mowing head's mounting hole.
28
WARNING
Wear protective gloves to reduce the
risk of direct contact with the sharp
cutting edges.
Mount only one metal cutting
attachment.
FS 91, FS 91 R
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