STIHL FS 100 RX Owner's Manual
STIHL FS 100 RX
Warning!
Read and follow all safety
precautions in Instruction Manual –
improper use can cause serious or
fatal injury.
Advertencia!
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 - 41
Manual de instrucciones
42 - 87
Contents
English
Guide to Using this Manual 2
Safety Precautions and Working
Techniques 3
Approved Combinations of Cutting
Attachment, Deflector, Handle and
Harness 15
Mounting the Loop Handle 16
Adjusting the Throttle Cable 16
Fitting the Carrying Ring 17
Original Instruction ManualPrinted on chlorine-free paper
Mounting the Cutting Attachment 17
4-MIX Engine 19
Fuel 19
Fueling 20
Fitting the Harness 22
Balancing the Trimmer/Brushcutter 22
Starting / Stopping the Engine 23
Operating Instructions 25
Cleaning the Air Filter 25
Engine Management 25
Adjusting the Carburetor 26
Spark Arresting Screen in Muffler 27
Spark Plug 28
Printing inks contain vegetable oils, paper can be recycled.
Lubricating the Gearbox 29
Replacing the Starter Rope and
Rewind Spring 29
Storing the Machine 31
Maintenance and Care 32
Main Parts 34
Specifications 35
Special Accessories 36
Maintenance and Repairs 36
STIHL Incorporated Federal
Emission Control Warranty
Statement 37
STIHL Incorporated California
Exhaust and Evaporative
Emissions Control Warranty
Statement 39
Trademarks 41
Allow only persons who fully understand
this manual to operate your trimmer.
To receive maximum performance and
satisfaction from your STIHL trimmer, 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. 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 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, handle and harness for
the type of cutting attachment being
used. Always wear proper eye
protection.
{
© ANDREAS STIHL AG & Co. KG, 2011
0458-259-8621-C. M7.H11.CP.
0000000733_003_GB
FS 100 RX
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 decompression valve
Manual fuel pump
Press to operate manual
fuel pump
Symbols in Text
Many operating and safety instructions
are supported by illustrations.
The individual steps or procedures
described in the manual may be marked
in different ways:
N A bullet marks 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. Example:
N Loosen the screw (1).
N Lever (2) ...
In addition to the operating instructions,
this manual may contain paragraphs
that require your special attention. Such
paragraphs are marked with the
symbols and signal words described
below:
Danger!
Indicates an imminent risk of severe or
fatal injury.
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 for assistance.
Filler hole for gear
lubricant
Air intake summer mode
Air intake winter mode
Handle heating
2
Warning!
Indicates a hazardous situation which, if
not avoided, could result in severe or
fatal injury.
Caution!
Indicates a risk of property damage,
including damage to the machine or its
individual components.
FS 100 RX
English
Safety Precautions and
Working Techniques
Because a trimmer is a
high-speed, fast-cutting
power tool, special safety
precautions must be
observed to reduce the
risk of personal 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 type of cutting attachments that 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.) 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 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. 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 this trimmer.
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. Thrown
objects, including broken heads or polymer blades, may result in serious or
fatal injury to the operator or
bystanders.
Use your trimmer equipped with the
appropriate cutting attachment only for
cutting grass 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. 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.
Safe use of a trimmer involves
1. the operator
2. the power tool
3. the use of the power tool
FS 100 RX
3
English
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
Warning!
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 100 RX
English
389BA019 KN
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 Z 87.1 (or your
applicable national standard.) 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.
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 gloves
when handling the
machine and metal
blades. Heavy-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.
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.
Good footing is very
important. Wear sturdy
boots with nonslip soles.
Steel-toed safety boots
are recommended.
THE POWER TOOL
For illustrations and definitions of the
power tool parts see the chapter on
"Main Parts."
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, Handle and Harness" in the instruction manual or the
STIHL "Power Tools and 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 line contact, never carry or
transport your power tool with the cutting attachment moving.
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.
FS 100 RX
5
English
001BA220 KN
Warning!
To reduce the risk of
burn injury, do not touch
hot parts of the machine
and the gear housing
when they are hot.
Warning!
Always shut off the engine and make
sure the cutting attachment has stopped
before putting a trimmer down. When
transporting it in a vehicle, properly
secure it to prevent turnover, fuel spillage and damage to the unit.
Fuel
Your STIHL power tool uses an oil-
gasoline mixture for fuel (see the
chapter on "Fuel" of your 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
combustible fuel vapor may escape
from the fuel system.
Fueling Instructions
Warning!
To reduce the risk of serious injury from
burns, never attempt to refuel the unit
until it has been completely removed
from the operator.
Warning!
Fuel your power tool in well-ventilated
areas, outdoors. Always shut off the
engine and allow it to cool before refueling. Gasoline vapor pressure may
build up inside the fuel tank depending
on the fuel used, the weather conditions
and the tank venting system.
In order to reduce the risk of burns and
other personal injury from escaping gas
vapor and fumes, remove the fuel filler
cap on your power tool carefully so as to
allow any pressure build-up in the tank
to release slowly. Never remove the fuel
filler cap while the engine is running.
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
machine.
Warning!
Check for fuel leakage
while refueling and during operation. If fuel
leakage is found, do not
start or run the engine
until the leak is fixed and
any spilled fuel has been wiped away.
Take care not to get fuel on your clothing. If this happens, change your
clothing immediately.
Different models may be equipped with
different fuel caps.
Toolless cap with grip
Warning!
In order to reduce the risk of fuel spillage and fire from an improperly
tightened fuel cap, correctly position
and tighten the fuel cap in the fuel tank
opening.
To do this with this STIHL cap, raise the
grip on the top of the cap until it is upright
at a 90° angle. Insert the cap in the fuel
tank opening with the raised positioning
marks on the grip of the cap and on the
fuel tank opening lining up. Using the
grip, press the cap down firmly while
turning it clockwise as far as it will go
(approx. 1/4 turn).
6
FS 100 RX
English
001BA227 KN
001BA226 KN
Fold the grip flush with
the top of the cap. Grip
the cap and check for
tightness. If the grip does
not lie completely flush
with the cap and the
detent on the grip does
not fit in the corresponding recess in the filler
opening, or if the cap is
loose in the filler opening,
the cap is not properly
seated and tightened and
you must repeat the
above steps.
Misaligned, damaged or broken cap
N If the cap does not drop fully into the
opening when the positioning marks
line up and/or if the cap does not
tighten properly when twisted, the
base of the cap may be prematurely
rotated (vis-à-vis the top) to the
closed position. Such misalignment
can result from handling, cleaning
or an improper attempt at
tightening.
Left: Base of cap in closed posi-
tion (with open space)
Right: Base of cap correctly posi-
tioned for installation
N To return the cap to the open
position for installation, turn the cap
(with the grip up) until it drops fully
into the tank opening. Next, twist the
cap counterclockwise as far as it will
go (approx. 1/4 turn) – this will twist
the base of the cap into the correct
position. Then, twist the cap
clockwise, closing it normally.
N If your cap still does not tighten
properly, it may be damaged or
broken; immediately stop use of the
unit and take it to your authorized
STIHL dealer for repair.
Screw Cap
Warning!
Unit vibrations can cause
an improperly tightened
fuel filler cap to loosen or
come off and spill quantities of fuel. In order to
reduce the risk of fuel
spillage and fire, tighten the fuel filler
cap by hand as securely as possible.
See also the "Fueling" chapter in your
Instruction Manual for additional
information.
Before Starting
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. Never use a power tool
that is damaged or not properly
maintained.
Warning!
Do not attach 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 in safe operating
condition. Inspect for loose parts (nuts,
screws, etc.) Replace damaged heads
before using the power tool.
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.
FS 100 RX
7
English
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!
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, handle and harness for the type of cutting
attachment being used (see chart in the
chapter on "Approved Combinations of
Cutting Attachment, Deflector, Handle
and 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 (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 the hand grip and harness (if you
are wearing one) 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,
practise releasing the unit from the
harness as quickly as possible.
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 if you are using one (see
appropriate chapter of the instruction
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.
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.
8
FS 100 RX
If you cannot set the correct idle speed,
002BA054 KN
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.
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.
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 attachment.
Never touch a moving cutting attachment 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.
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.
English
Warning!
As soon as the engine is
running, this product generates toxic exhaust
fumes containing chemicals, such as unburned
hydrocarbons (including
benzene) and carbon monoxide, that
are known to cause respiratory problems, cancer, birth defects, or other
reproductive harm. Some of the gases
(e.g. carbon monoxide) may be colorless and odorless. To reduce the risk of
serious or fatal injury / illness from inhaling toxic fumes, never run the machine
indoors or in poorly ventilated 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.
FS 100 RX
9
English
15m (50ft)
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
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 – move the slide
control / stop switch to 0 or STOP.
Warning!
The rotating cutting attachment may
fling foreign objects directly or by ricochet a great distance.
10
To reduce the risk of eye and other i njury
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. Any coworkers who must be
in the restricted area should also wear
goggles or protective glasses.
Stop the engine and cutting tool
immediately if you are approached.
Never use metal
blades on this trimmer. Only mowing
heads are
authorized.
Warning!
Before you start work,
examine the area for
stones, glass, fence wire,
metal, trash or other solid
objects. The cutting
attachment could throw
objects of this kind.
Warning!
This trimmer is normally to be used at
ground level with the cutting attachment
parallel to the ground. Use of a trimmer
above ground level or with the cutting
attachment perpendicular to the ground
may increase the risk of injury, since the
cutting attachment is more fully exposed
and the power tool may be more difficult
to control.
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 head for cracks, wear
and damage.
Warning!
A loose head may vibrate, crack, break
or come off the trimmer, 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 head loosens after
being properly tightened, stop work
immediately. The retaining nut may be
worn or damaged and should be
replaced. If the head continues to
loosen, see your STIHL dealer. Never
use a trimmer with a loose cutting
attachment.
FS 100 RX
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!
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.
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.
Warning!
To reduce the risk of fire and burn injury,
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!
Never modify your muffler. The muffler
could be damaged and cause an
increase in heat radiation or sparks,
thereby increasing the risk of fire and
burn injury. You may also permanently
damage the engine. Have your muffler
serviced and repaired by your STIHL
servicing dealer only.
English
Catalytic Converter
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 conventional mufflers when
the engine returns to idle or is shut off.
To reduce the risk of fire and burn injuries, the following specific safety
precautions must be observed.
Warning!
Since a muffler with a catalytic converter
cools down less rapidly than conventional mufflers, 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 materials while it is still hot.
Warning!
An improperly mounted or damaged cylinder housing or a damaged / deformed
muffler shell may interfere with the cooling process of the catalytic converter.
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 catalytic converter is furnished with
screens designed to reduce the risk of
fire from the emission of hot particles.
Due to the heat from the catalytic
reaction, these screens will normally
FS 100 RX
11
English
000BA019 KN
stay clean 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.
Using the Cutting Attachments
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 this trimmer.
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.
Mowing heads are to be used only on
trimmers 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 cord 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 20-3
Uses either nylon lines or nonrigid,
pivoting polymer blades.
12
FS 100 RX
Warning!
002BA177 KN
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.
Warning!
If the wear limit marks are ignored, there
is a risk of the cutting attachment shattering and flying parts injuring the
operator or bystanders. To reduce the
risk of accidents from shattered blades,
avoid contact with stones, metal and
similar solid objects. Check PolyCut
blades for cracks at regular intervals. If
a crack is found on one blade, always
replace all blades.
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.
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 or if nonapproved replacement
parts were used, 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.
English
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.
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.
FS 100 RX
13
English
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. If your muffler was equipped with a
spark-arresting screen to reduce the
risk of fire, never operate your power
tool if the screen is missing or damaged.
Remember that the risk of forest fires is
greater in hot or dry weather.
Warning!
Never repair damaged or broken heads.
This may cause parts of the cutting
attachment to come off and result in
serious or fatal injuries.
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.
14
FS 100 RX
Approved Combinations of Cutting Attachment, Deflector, Handle and Harness
1
2
3
4
5
6
7
9
10
8
681BA138 KN
Cutting attachment Deflector Handle Harness
English
Approved Combinations
The complete combination includes:
– Cutting attachment
– Deflector
– Handle
– Harness
Select correct combination from the
table according to the cutting
attachment you intend to use. Read the
table horizontally from left to right.
Cutting Attachments
Mowing heads
1 STIHL SuperCut 20-2
FS 100 RX
2 STIHL AutoCut C 25--2
3 STIHL AutoCut 25-2
4 STIHL TrimCut 31-2
5 STIHL FixCut 25-2
6 STIHL PolyCut 20-3
Deflector
7 Deflector only for mowing heads
Handles
8 Loop handle
Harnesses
9 Shoulder strap may be used
10 Full harness may be used
15
English
002BA163 KN
2
1
002BA161 KN
Warning!
Based on the cutting attachment being
used:
Choose the proper deflector in order to
reduce the risk of 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 injury from loss of control and contact with the cutting
attachment.
Only mowing heads with nylon blades or
polymer blades may be used on trimmers with loop-handle without barrier
bar.
Do not use rigid polymer blades, metal
cutting attachments or circular saw
blades on this unit.
Mounting the Loop Handle Adjusting the Throttle Cable
A properly adjusted throttle cable is the
precondition for correct operation in the
full throttle, starting throttle and idle
positions.
N Adjust the throttle cable only when
the unit is completely and properly
assembled.
N Use a suitable tool to push the slide
to the end of the slot (see
N Secure the loop handle (1)
approx. 8 in (20 cm) (A) forward of
the control handle (2).
N Adjusting the loop handle
N Tighten down the screws firmly.
The sleeve (3) must be between the
loop handle and the control handle.
illustration).
16
N Press down the throttle trigger
lockout (1) and squeeze the throttle
trigger (2) (full throttle) – this sets
the throttle cable correctly.
FS 100 RX
English
002BA142 KN
1
2
1
259BA012 KN
Fitting the Carrying Ring
The carrying ring comes standard with
the machine or is available as a special
accessory.
For position of carrying ring see "Main
Parts".
N Place the clamp (1) against the
drive tube with the tapped hole on
the left (viewed from engine).
N Squeeze the two ends of the clamp
together and hold in that position.
N Insert the M6x14 screw (2).
N Line up the carrying ring.
N Tighten down the screw firmly.
Mounting the Cutting
Attachment
Preparations
N Lay your brushcutter on its back so
that the cutting attachment
mounting face is facing up.
Block the drive shaft.
N Insert the stop pin (2) or screwdriver
– come standard with machine or
are available as special accessories
– in the hole (3) in the gearbox as far
as stop, and apply slight pressure.
N Rotate the nut or cutting attachment
on the shaft (1) until the stop pin
slips into position and blocks the
shaft.
After mounting the cutting attachment,
remove the tool used to block the shaft.
Mounting the mowing head
Keep the instruction sheet for the
mowing head in a safe place.
STIHL PolyCut 20-3
Install only the mowing head with a
double-stepped seat as shown above.
FS 100 RX
17
English
STIHL SuperCut 20-2,
STIHL AutoCut 25-2,
STIHL AutoCut C 25-2,
STIHL TrimCut 31-2, STIHL FixCut 252, STIHL PolyCut 20-3
N Screw the mowing head
counterclockwise on to the shaft (1)
as far as stop.
N Block the drive shaft.
N Tighten down the mowing head.
Remove the tool used to block the shaft.
STIHL SuperCut 20-2,
STIHL AutoCut 25-2,
STIHL AutoCut C 25-2,
STIHL TrimCut 31-2, STIHL FixCut 252, STIHL PolyCut 20-3
N Unscrew the mowing head
clockwise.
Adjusting Nylon Line
STIHL SuperCut
Fresh line is advanced automatically if
the remaining line is still at least 21/2in.
(6 cm) long. The blade on the deflector
trims surplus line to the correct length.
STIHL AutoCut
N Hold the rotating mowing head
above the ground – tap it on the
ground once – about 11/4in (3cm)
fresh line is advanced.
The blade on the deflector trims surplus
line to the correct length – avoid tapping
the mowing head more than once at a
time.
Line feed operates only if both lines still
have a minimum length of 1 in (2.5 cm).
All other mowing heads
Refer to the instructions supplied with
the mowing head.
Replacing Nylon Line or Cutting Blades
Refer to the instructions supplied with
the mowing head.
Removing the mowing head
N Block the drive shaft.
18
To reduce the risk of injury, always shut
off the engine before adjusting the
mowing line by hand.
FS 100 RX
English
4-MIX Engine Fuel
The STIHL 4-MIX engine features
mixture lubrication and must be run on a
fuel mixture of gasoline and engine oil.
It operates otherwise on the 4-stroke
principle.
This engine is certified to operate on
unleaded gasoline and the STIHL twostroke engine oil at a mix ratio of 50:1.
Your engine requires a mixture of highquality gasoline and two-stroke air
cooled engine oil.
Use mid-grade unleaded gasoline with a
minimum octane rating of 89 (R+M/2)
and no more than 10% ethanol content.
Fuel with a lower octane rating may
increase engine temperatures. This, in
turn, increases the risk of 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 and
catalytic converters as well. This could
cause running problems or even
damage the engine. For this reason
STIHL recommends that you use only
high-quality unleaded gasoline!
Gasoline with an ethanol content of
more than 10% can cause running
problems and major damage in engines
with a manually adjustable carburetor
and should not be used in such engines.
The ethanol content in gasoline affects
engine running speed – it may be
necessary to readjust the carburetor if
you use fuels with various ethanol
contents.
Warning!
To reduce the risk of personal injury
from loss of control and / or contact with
the running cutting tool, do not use your
unit with incorrect idle adjustment. At
correct idle speed, the cutting tool
should not move.
If your power tool shows an incorrect
idle adjustment, have your STIHL dealer
check your power tool and make proper
adjustments and repairs.
The idle speed and maximum speed of
the engine change if you switch from a
fuel with a certain ethanol content to
another fuel with a much higher or lower
ethanol content.
This problem can be avoided by always
using fuel with the same ethanol
content.
Use only STIHL two-stroke engine oil or
equivalent high-quality two-stroke
engine oils that are designed for use
only in air cooled two-cycle engines.
We recommend STIHL HP Ultra 2-Cycle
Engine Oil since it is specially
formulated for use in STIHL engines.
Do not use BIA or TCW rated (twostroke water cooled) mix oils or other
mix oils that state they are for use in both
water cooled and air cooled engines
(e.g., outboard motors, snowmobiles,
chain saws, mopeds, etc.).
Take care when handling gasoline.
Avoid direct contact with the skin and
avoid inhaling fuel vapor. When filling at
the pump, first remove the container
from your vehicle and place the
container on the ground before filling. To
reduce the risk of sparks from static
FS 100 RX
19
English
002BA420 KN
002BA418 KN
002BA419 KN
249BA053 KN
249BA054 KN
discharge and resulting fire and/or
explosion, do not fill fuel containers that
are sitting in or on a vehicle or trailer.
The container should be kept tightly
closed in order to limit the amount of
moisture that gets into the mixture.
The machine‘s fuel tank should be
cleaned as necessary.
Fuel mix ages
Only mix sufficient fuel for a few days
work, not to exceed 3 months of storage.
Store in approved fuel-containers only.
When mixing, pour oil into the container
first, and then add gasoline. Close the
container and shake it vigorously by
hand to ensure proper mixing of the oil
with the fuel.
Gasoline
Oil (STIHL 50:1 or equivalent high-quality oils)
US gal. US fl.oz.
12.6
2 1/2 6.4
512.8
Dispose of empty mixing-oil containers
only at authorized disposal locations.
Fueling
Preparations
N Before fueling, clean the filler cap
and the area around it so that dirt
cannot fall into the tank.
N Always position the machine so that
the filler cap is facing upwards.
One of two different filler caps is
installed as standard at the factory.
Threaded filler cap
Opening the toolless filler cap
N Swing the grip into an upright
position.
20
Toolless filler cap (with folding grip)
N Turn the cap counterclockwise
(approx. 1/4 turn).
N Remove the filler cap.
FS 100 RX
English
249BA055 KN
249BA056 KN
200BA421 KN
200BA422 KN
Refueling
Take care not to spill fuel while fueling,
and do not overfill the tank. STIHL
recommends use of the STIHL filling
system (special accessory).
Closing the toolless filler cap
N Position the cap with the grip in an
upright position; the raised
positioning marks must line up.
N Turn cap clockwise as far as it will
go (approx. 1/4 turn).
described above must be repeated. See
also the "Toolless cap with grip" section
in the Safety Precautions.
Opening the threaded filler cap
N Turn the cap counterclockwise until
it can be removed from the tank
opening.
N Remove the filler cap.
Refueling
Take care not to spill fuel while fueling
and do not overfill the tank. STIHL
recommends use of the STIHL filling
system (special accessory).
Closing the threaded filler cap
N Position cap.
N Turn the cap clockwise as far as it
will go and tighten it as securely as
possible by hand.
N Fold the grip down so that it is flush
with the surface.
If the grip is not flush with the surface
and the lug on the clip does not engage
entirely in the recess (arrow), the cap is
not properly closed and the steps
FS 100 RX
21
English
1
259BA016 KN
2
1
2
1
2
002BA311 KN
1
2
1
2
002BA312 KN
Fitting the Harness
The type and style of the harness
depend on the market.
The use of the harness is described in
the chapter on "Approved Combinations
of Cutting Attachment, Deflector, Handle
and Harness".
Shoulder strap
Balancing the
Trimmer/Brushcutter
Attaching the unit to the harness
The type and style of the harness and
carabiner (spring hook) depend on the
market.
N Attach the carabiner (1) to the
carrying ring (2) on the drive tube.
Balance the brushcutter.
N Adjust the carrying ring.
N Tighten the screw moderately.
N Let go of the brushcutter and check
to see ho w it is balance – the cutting
tool should just touch the ground in
the normal working position.
N Move the carrying ring as required.
When the correct floating position has
been reached:
N Tighten down the screw on the
carrying ring firmly.
Detaching the unit from the harness
N Put on the shoulder strap (1).
N Adjust the length of the strap so that
the carabiner (2) is level with your
right hip when the machine is
attached.
N Balance the brushcutter.
22
N Press down the bar on the
carabiner (1) and pull the carrying
ring (2) out of the carabiner.
N Loosen the screw (3).
FS 100 RX
English
3
STOP
2
5
6
4
7
002BA181 KN
START
STOP-
1
249BA057 KN
9
8
552BA014 KN
552BA015 KN
Starting / Stopping the
Engine
Control handle
Controls
Symbol on slide control
7 h – stop symbol and arrow. To stop
the engine, push the slide control in
the direction of the arrow on the stop
symbol (h) to STOP-0.
Starting
N Press down the trigger lockout lever
and squeeze the throttle trigger.
N and hold them in that position.
N Move the slide control to START
and hold it there.
N Now release the throttle trigger,
slide control and trigger lockout in
that order. This is the starting
throttle position.
g if the engine is cold
e for warm start – also use this posi-
tion if the engine has been running
but is still cold.
N Press the fuel pump bulb (9) at least
five times – even if the bulb is filled
with fuel.
Starting
1 Throttle trigger lockout
2 Throttle trigger
3 Slide control
Positions of slide control
4STOP-0 – engine off – the ignition is
5 F – normal run position – the engine
6START – the ignition is switched on
switched off
is running or can start
– the engine can start
FS 100 RX
N Set the choke knob (8):
N Place the unit on the ground: It must
rest securely on the engine support
and the deflector. Check that the
cutting attachment is not touching
the ground or any other obstacles.
N Make sure you have a safe and
secure footing.
N Hold the unit with your left hand and
press it down firmly – your thumb
should be under the fan housing.
Do not stand or kneel on the drive tube.
23
English
552BA016 KN
N Hold the starter grip with your right
hand.
N Pull the starter grip slowly until you
feel it engage and then give it a brisk
strong pull.
Do not pull out the starter rope all the
way – it might otherwise break.
N Do not let the starter grip snap back.
Guide it slowly back into the housing
so that the starter rope can rewind
properly.
N Crank the engine until it begins to
fire. After no more than five
attempts, turn the choke knob to e.
N Continue cranking.
As soon as the engine runs
N Blip the throttle trigger. The slide
control moves to the normal run
position F – and the engine settles
down to idle speed.
Shut off the engine.
N Push the slide control in the
direction of the arrow on the stop
symbol (h) to STOP-0.
At very low outside temperatures:
As soon as the engine runs:
N Blip the throttle trigger to disengage
the starting throttle position. The
slide control moves to the normal
run position (F) – and the engine
settles down to idle speed.
N Open the throttle slightly.
N Warm up the engine for a short
period.
If the engine does not start
Choke knob
If you did not turn the choke knob to e
quickly enough after the engine began to
fire, the combustion chamber is flooded.
N Turn the choke knob to e.
N Set the slide control, lockout lever
and throttle trigger to the starting
throttle position.
N Start the engine by pulling the
starter rope briskly – 10 to 20 pulls
may be necessary.
N Crank the engine several times with
the starter to clear the combustion
chamber.
N Refit the spark plug – see "Spark
Plug".
N Move the slide control to START.
N Set the choke knob to e – even if
the engine is cold.
N Now start the engine.
Throttle cable adjustment
N Check adjustment of throttle cable –
see chapter on "Adjusting the
Throttle Cable".
Fuel tank run until completely dry
N After refueling, press the fuel pump
bulb at least five times – even if the
bulb is filled with fuel.
N Set the choke knob according to
engine temperature.
N Start the engine.
Make sure the carburetor is correctly
adjusted. The cutting attachment must
not rotate when the engine is idling.
Your machine is now ready for
operation.
24
If the engine still does not start
N Move the slide control to STOP-0.
N Remove the spark plug – see
"Spark Plug".
N Dry the spark plug.
FS 100 RX
English
1
273BA006 KN
2
4
Operating Instructions Cleaning the Air Filter
During 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
unnecessary 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
engine are greater during this period.
The engine develops its maximum
power after about 5 to 15 tank fillings.
During Operation
After a long period of full throttle
operation, allow the engine to run for a
short while at idle speed so that engine
heat can be dissipated by the flow of
cooling air. This protects enginemounted components (ignition,
carburetor) from thermal overload.
After Finishing Work
Storing for a short period: Wait for the
engine to cool down. Empty the fuel tank
and keep the machine in a dry place,
well away from sources of ignition, until
you need it again. For longer out-ofservice periods – see "Storing the
Machine".
If there is a noticeable loss of engine
power
N Turn the choke knob to g
N Take out the screw (1) and remove
the filter cover (2).
N Clean away loose dirt from around
the filter.
N Grip the filter element (3) at the
cutout (arrow) in the filter
housing (4) and remove it.
N Fit a new filter element. As a
temporary measure you can knock it
out on the palm of your hand or blow
it out with compressed air. Do not
wash.
N Replace damaged parts.
Installing the filter
N Install the filter element in the filter
housing and fit the cover.
N Insert the screw and tighten it down
firmly.
Engine Management
Exhaust emissions are controlled by the
design of the fundamental engine
parameters and components (e.g.
carburation, ignition, timing and valve or
port timing) without the addition of any
major hardware.
FS 100 RX
25
English
249BA051 KN
Adjusting the Carburetor
The carburetor comes from the factory
with a standard setting.
This setting provides an optimum fuel-air
mixture under most operating
conditions.
With this carburetor it is only possible to
adjust the high speed and low speed
screws within fine limits.
Standard Setting
N Shut off the engine.
N Mount approved cutting tool or
attachment.
N Check the air filter and clean or
replace as necessary.
N Check that the throttle cable is
properly adjusted – readjust if
necessary – see chapter on
"Adjusting the Throttle Cable".
N Check the spark arresting screen
and clean or replace as necessary.
N Carefully turn both adjusting screws
counterclockwise as far as stop:
– The high speed screw (H) is 3/4 turn
open.
– The low speed screw (H) is 3/4 turn
open.
N Start and warm up the engine.
N Adjust idle speed with the idle speed
screw (LA) so that the cutting
attachment does not move.
Rule of thumb:
Turn the high speed screw (H) about
one quarter of a turn for every 3300 ft
(1000 m) change in altitude.
Conditions for adjustment
N Carry out the standard setting
without disturbing the high speed
screw (H).
N Warm up the engine for about 3
minutes.
N Open the throttle wide.
At high altitude
N Turn the high speed screw (H)
clockwise (leaner), no further than
stop, until there is no further
noticeable increase in engine
speed.
At sea level
N Turn the high speed screw (H)
counterclockwise (richer), no further
than stop, until there is no further
noticeable increase in engine
speed.
It is possible that maximum engine
speed may be reached with the standard
setting in each case.
26
Fine Tuning
A slight correction of the setting of the
high speed screw (H) may be necessary
if engine power is not satisfactory when
operating at high altitude, sea level or
after changing the working tool.
Readjust idle
It is usually necessary to change the
setting of the idle speed screw (LA) after
every correction to the low speed
screw (L).
N Warm up the engine for about 3
minutes.
FS 100 RX
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