Stihl STIHL FS 40, 50 STIHL FS 40, 50 (en)
STIHL FS 40, 50
Instruction Manual
Contents
English
Guide to Using this Manual 2
Safety Precautions and Working
Techniques 2
Approved Combinations of Cutting
Attachment, Deflector, Handle and
Harness 9
Mounting the Loop Handle 10
Mounting the Deflector 10
Mounting the Cutting Attachment 11
Original Instruction ManualPrinted on chlorine-free paper
Fuel 13
Fueling 14
Starting / Stopping the Engine 15
Operating Instructions 17
Cleaning the Air Filter 17
Adjusting the Carburetor 18
Spark Plug 18
Engine Running Behavior 19
Storing the Machine 19
Maintaining the Mowing Head 20
Maintenance and Care 24
Minimize Wear and Avoid Damage 25
Main Parts 26
Printing inks contain vegetable oils, paper can be recycled.
Specifications 27
Maintenance and Repairs 28
Disposal 28
EC Declaration of Conformity 29
UKCA Declaration of Conformity 29
Dear Customer,
Thank you for choosing a quality
engineered STIHL product.
It has been built using modern
production techniques and
comprehensive quality assurance.
Every effort has been made to ensure
your satisfaction and trouble-free use of
the product.
Please contact your dealer or our sales
company if you have any queries
concerning this product.
Your
Dr. Nikolas Stihl
© ANDREAS STIHL AG & Co. KG, 2021
0458-546-0121-E. VA0.H21.
0000001049_031_GB
FS 40, FS 40 C, FS 50, FS 50 C
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 the machine are explained in
this manual.
Depending on the model concerned, the
following pictograms may be attached to
your machine.
Fuel tank; fuel mixture of
gasoline and engine oil
Operate decompression
valve
Manual fuel pump
Operate manual fuel
pump
Tube of grease
Intake air: Summer
operation
Intake air: Winter
operation
Handle heating
Symbols in text
WARNING
Warning where there is a risk of an
accident or personal injury or serious
damage to property.
NOTICE
Caution where there is a risk of
damaging the machine or its individual
components.
Engineering improvements
STIHL's philosophy is to continually
improve all of its products. For this
reason we may modify the design,
engineering and appearance of our
products periodically.
Therefore, some changes, modifications
and improvements may not be covered
in this manual.
Safety Precautions and
Working Techniques
Because the machine 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 and understand the
User Manual before commissioning and keep it in
a safe place for future reference. Non-compliance
with the User Manual
may cause serious or
even fatal injury.
Observe all applicable local safety
regulations, e.g. by trade organizations,
social insurance institutions, labor safety
authorities etc.
If you have never used a power tool
before: Have your dealer or other
experienced user show you how to
operate your machine – or attend a
special course to learn how to operate it.
Minors should never be allowed to use
the machine – except for apprentices
over the age of 16 when working under
supervision.
Children, animals and onlookers must
not be allowed near the machine.
When not using the machine, it must be
laid down in such a way that it does not
endanger anyone. Ensure that the
machine cannot be used without
authorization.
2
FS 40, FS 40 C, FS 50, FS 50 C
English
546BA001 KN
The user is responsible for accidents or
risks involving third parties or their
property.
Lend or rent your power tool only
together with this User Manual and only
to persons who are familiar with this
model and its operation.
The use of noise-emitting power tools
may be restricted to certain times by
national or local regulations.
Anyone operating the machine must be
well rested, in good physical health and
in good mental condition. If you have
any condition that might be aggravated
by strenuous work, check with your
doctor before operating a machine.
If you have a pacemaker: The ignition
system of your machine produces an
electromagnetic field of very low
intensity. This field may interfere with
some pacemakers. STIHL recommends
that persons with pacemakers consult
their physician and the pacemaker
manufacturer to reduce any health risk.
Anyone who has consumed alcohol or
drugs or medicines affecting their ability
to react must not operate a power tool.
Depending on the cutting attachment
fitted, use your tool only for cutting
grass, undergrowth and similar
materials.
Other uses are not permitted and may
lead to accidents or damage to the
machine. Never attempt to modify your
power tool in any way since this may
result in accidents or damage to the
machine.
Only use cutting attachments and
accessories that are explicitly approved
for this power tool model by STIHL or
are technically identical. If you have any
questions in this respect, consult your
dealer. Use only high-quality parts and
accessories. in order to avoid the risk of
accidents and damage to the machine.
STIHL recommends the use of genuine
STIHL tools and accessories. They are
specifically designed to match the
product and meet your performance
requirements.
The guard provided with your machine
may not protect the operator from all
foreign objects (gravel, glass, wire etc.)
ejected by the revolving cutting
attachment. Ejected objects may also
ricochet and strike the operator.
Clothing and equipment
Wear proper protective clothing and
equipment.
Clothing must be robust
but allow complete freedom of movement. Wear
close-fitting clothes such
as a boiler suit, not a
loose jacket.
Do not wear clothing which could
become trapped in wood, brush or
moving parts of the machine. Do not
wear a scarf, necktie or jewelry. Tie up
and confine long hair above your
shoulders.
Wear sturdy shoes with
non-slip soles.
WARNING
To reduce the risk of eye
injuries, wear close-fitting safety glasses in
accordance with European Standard EN 166.
Make sure the safety
glasses are a snug fit.
Wear face protection and make sure it is
a good fit. Face protection alone is not
sufficient to protect the eyes.
Wear "personal" sound protection, e.g.
ear defenders.
Wear sturdy protective
gloves made of a resistant material (e.g.
leather).
STIHL can supply a comprehensive
range of personal protective equipment.
Transporting the machine
Always stop the engine.
Carry the unit properly balanced by the
shaft or loop handle.
FS 40, FS 40 C, FS 50, FS 50 C
3
English
By vehicle: When transporting in a
vehicle, properly secure your machine to
prevent turnover, damage and fuel
spillage.
Refueling
Gasoline is highly flammable – keep away from
fire or flame – do not spill
any fuel – no smoking.
Always shut off the engine before
refueling.
Do not fuel a hot engine – fuel may spill
and cause a fire.
Open the fuel cap carefully to allow any
pressure build-up in the tank to release
slowly and avoid fuel spillage.
Only refuel the machine in a well
ventilated place. If fuel has been spilled,
immediately clean the machine – do not
allow your clothes to be splashed with
fuel. If that happens, change your
clothes at once.
After refueling, close the
fuel cap as tightly as
possible.
This helps reduce the risk of unit
vibrations causing an incorrectly
tightened fuel cap to loosen or come off
and spill quantities of fuel.
Check for leaks. Do not start the engine
if there is a fuel leak – serious or fatal
burns could result!
Before starting
Check that your power tool is properly
assembled and in good condition – refer
to appropriate chapters in the User
Manual.
– Check the fuel system for leaks,
especially the visible parts, e. g.,
fuel cap, hose connections, manual
fuel pump (only in machines with a
manual fuel pump). In case of
leakage and damage, do not start
the engine – risk of fire! Have the
machine serviced by a dealer
before using it
– Use only an approved combination
of cutting attachment, deflector,
handle and harness. All parts must
be assembled properly and
securely. To reduce the risk of
injury, never use metal cutting
attachments!
– The stop switch must move easily to
0.
– Check the choke lever, throttle
trigger and throttle trigger lockout
for smooth action - throttle trigger
must return automatically to idle
position. The choke lever must
spring back from the g and <
positions to the run position F when
the throttle trigger lockout and
throttle trigger are squeezed.
– Check that the spark plug boot is
secure – a loose boot may cause
sparking that could ignite
combustible fumes and cause a fire!
– Check cutting attachment for
correct and secure assembly and
good condition
– Check safety devices (e. g.,
deflector for cutting attachments) for
damage and/or wear. Always
replace damaged parts. Never
operate the unit with a damaged
deflector
– Never attempt to modify the controls
or safety devices.
– Keep the handles dry and clean –
free from oil and dirt – this is
important for safe control of the
machine
– Adjust the harness and handle(s) to
suit your height and reach
To reduce the risk of personal injury, do
not operate your power tool if it is
damaged or not properly assembled!
To prepare for emergencies when using
a harness: Practice setting down the
machine quickly. To avoid damage, do
not throw the machine to the ground
when practicing.
Starting the engine
Start the engine at least 3 meters from
the fueling spot, outdoors only.
Place the unit on firm ground in an open
area. Make sure you have a stable and
secure footing. Hold the unit securely.
The cutting attachment must be clear of
the ground and all other obstructions
because it may begin to run when the
engine starts.
Your power tool is a one-person unit. To
reduce the risk of injury from ejected
objects, do not allow other persons
within a radius of 15 meters of your own
position – even when starting.
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FS 40, FS 40 C, FS 50, FS 50 C
English
546BA002 KN
15m (50ft)
Avoid contact with the
cutting attachment – risk
of injury!
Do not drop-start the engine – start it as
described in the User Manual.
The cutting attachment
runs on for a short while
after releasing the throttle
trigger – coasting effect!
Check engine idling: The cutting
attachment must remain at a standstill
when the engine idles – throttle trigger
released.
To reduce the risk of fire, keep hot
exhaust gases and hot muffler away
from easily combustible materials (e.g.
wood chips, bark, dry grass, fuel).
Holding and guiding the machine
Always hold the unit firmly with both
hands on the handles. Make sure you
always have a firm and secure footing.
Left hand on loop handle, right hand on
control handle, even if you are lefthanded.
FS 40, FS 40 C, FS 50, FS 50 C
While working
In the event of impending danger or in
an emergency, switch off the engine
immediately – move the stop switch in
the direction of 0.
There is a risk of accident from ejected
objects within a wide area around the
working space, so you must ensure that
there is no-one within a 15 m radius of
the machine. This distance must also be
maintained in relation to objects
(vehicles, window panes) – risk of
property damage! Even at distances
beyond 15 m, the danger cannot be
ruled out.
Check that the engine is properly idling
so that the cutting tool will not continue
rotating after you release the throttle
trigger.
Check and correct the idle speed setting
at regular intervals. If the cutting
attachment still rotates at idle speed,
have your dealer make proper
adjustments or repairs. STIHL
recommends you have this work done
by a STIHL servicing dealer.
Take special care in slippery conditions
– damp, snow, ice, on slopes or uneven
ground.
Watch out for obstacles: tree stumps,
roots – risk of tripping or stumbling!
Make sure you always have a firm and
secure footing.
Only work while standing on the ground,
never on a ladder, work platform or other
unstable surface.
More care and attention than usual are
required when wearing ear protection,
as sounds warning you of impending
danger (shouts, beeps, etc.) cannot be
heard properly.
Take breaks when you start getting tired
or feeling fatigue – risk of accidents!
Work calmly and carefully – in daylight
conditions and only when visibility is
good. Proceed with caution, do not put
others in danger.
As soon as the engine is
running, the power
machine generates toxic
exhaust gas.As soon as
the engine is running, the
power machine generates toxic exhaust gas.
These gases may be
odorless and invisible
and may contain
unburned hydrocarbons
and benzene. Never run
the engine indoors or in
poorly ventilated locations, even if your model
is equipped with a catalytic converter.
To reduce the risk of serious or fatal
injury from breathing toxic fumes,
ensure proper ventilation when working
in trenches, hollows or other confined
locations.
Stop work immediately if you start
suffering from nausea, headaches,
impaired vision (e.g. your field of vision
5
English
gets smaller), impaired hearing,
dizziness, or impaired concentration –
these symptoms may possibly be the
result of too-high exhaust gas
concentration – Risk of accidents!
Operate your power tool so that it
produces a minimum of noise and
emissions – do not run the engine
unnecessarily, accelerate the engine
only when working.
To reduce the risk of fire, do not smoke
while operating or standing near your
power tool. Note that combustible fuel
vapor may escape from the fuel system.
Dusts, mist and fumes emissions during
the work may be hazardous to your
health. Wear respiratory protection in
case of heavy dust or smoke emission.
If your power 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 – see also
"Before Starting". Check in particular
that the fuel system has no leaks and the
safety equipment is fully operative.
Never use a power tool that is no longer
safe to operate. In case of doubt, contact
a dealer.
Do not operate your power tool with the
choke lever in the warm start position <
– the engine speed cannot be controlled
in this position.
Never work without protection
suitable for the
respective
machine and cutting tool – risk of
injury from ejected
objects!
Check the work site –
rocks, metal objects etc.
could get caught up and
ejected – potentially
beyond a distance of
15 m – risk of injury! Such
objects can also damage
the cutting attachment
and other property (e.g.
parked vehicles,
windows).
Be particularly careful when working on
difficult, densely grown terrain.
When mowing in tall scrub, under
shrubbery and hedges: Hold the cutting
tool at a working height of at least 15 cm
– this avoids risks to animals.
Always shut off the engine before
leaving the unit unattended.
Check the cutting tool regularly at
frequent intervals, and immediately if
you notice a change in its behavior:
– Stop the engine, hold the machine
securely, allow the cutting
attachment to come to a stop
– Check condition and tightness of
connections, look out for fine cracks
– Immediately replace defective
cutting tools, also in case of minor
hairline cracks
Clean grass and plant residue off the
cutting attachment mounting at regular
intervals – remove any accumulated
material from the cutting attachment and
deflector.
To reduce the risk of injury, shut off the
engine before replacing the cutting
attachment.
Do not continue using or attempt to
repair damaged or cracked cutting
attachments by means of welding,
straightening or modifying the shape
(unbalanced).
Particles or pieces may come off and hit
the operator or a bystander at a high
speed – risk of most severe injuries!
If a rotating cutting attachment touches a
rock or another hard object, sparks may
be generated which may possibly ignite
combustible materials. Also dried-out
plants and brushwood are combustible,
above all in hot and dry weather. If there
is a risk of fire, do not use cutting
attachments in the vicinity of
combustible materials, dried-out plants
or brushwood. It is mandatory that you
ask the responsible forestry office about
current fire hazards.
Using mowing heads
Only use the deflector with a properly
mounted blade that ensures the mowing
line is restricted to the permissible
length.
Always switch off the engine to adjust
the mowing line for manually adjustable
mowing heads – risk of injury!
Misuse with mowing lines that are too
long reduces the working speed of the
engine. The constant slipping of the
clutch causes overheating and damage
to important components (e.g. clutch,
plastic housing parts) – e.g. due to the
cutting attachment rotating during idling
– risk of injury!
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FS 40, FS 40 C, FS 50, FS 50 C
English
Vibrations
Prolonged use of the power tool may
result in vibration-induced circulation
problems in the hands (whitefinger
disease).
No general recommendation can be
given for the length of usage because it
depends on several factors.
The period of usage is prolonged by:
– Hand protection (wearing warm
gloves)
– Work breaks
The period of usage is shortened by:
– Any personal tendency to suffer
from poor circulation (symptoms:
frequently cold fingers, tingling
sensations).
– Low outside temperatures.
– The force with which the handles
are held (a tight grip restricts
circulation).
Continual and regular users should
monitor closely the condition of their
hands and fingers. If any of the above
symptoms appear (e.g. tingling
sensation in fingers), seek medical
advice.
Maintenance and Repairs
Service the machine regularly. Do not
attempt any maintenance or repair work
not described in the instruction manual.
Have all other work performed by a
servicing dealer.
STIHL recommends that you have
servicing and repair work carried out
exclusively by an authorized STIHL
servicing dealer. STIHL dealers are
regularly given the opportunity to attend
training courses and are supplied with
the necessary technical information.
Only use high-quality replacement parts
in order to avoid the risk of accidents
and damage to the machine. If you have
any questions in this respect, consult a
servicing dealer.
STIHL recommends the use of genuine
STIHL replacement parts. These parts
are specifically designed to match your
machine model and meet your
performance requirements.
To reduce the risk of injury from
unintentional engine startup, always
shut off the engine and disconnect the
spark plug boot before performing any
repairs, maintenance or cleaning work. –
Exception: Carburetor and idle speed
adjustments.
Do not turn the engine over on the
starter with the spark plug boot or spark
plug removed since there is otherwise a
risk of fire from uncontained sparking.
To reduce the risk of fire, do not service
or store your machine near open flames.
Check the fuel filler cap for leaks at
regular intervals.
Use only a spark plug of the type
approved by STIHL and make sure it is
in good condition – see "Specifications".
Inspect the ignition lead (insulation in
good condition, secure connection).
Check the condition of the muffler.
To reduce the risk of fire and damage to
hearing, do not operate your machine if
the muffler is damaged or missing.
Do not touch a hot muffler since burn
injury will result.
Symbols on Deflectors
An arrow on the deflector shows the
correct direction of rotation of the cutting
attachments.
Use deflector in
combination with
mowing heads
only. Do not use
metal cutting
attachments.
FS 40, FS 40 C, FS 50, FS 50 C
7
English
000BA019 KN
1
002BA073 KN
2
002BA074 KN
Mowing Head with Nylon Lines
Nylon line achieves a soft cut for edging
and trimming around fence posts, trees,
etc. – less risk of damaging tree bark.
WARNING
To reduce the risk of injury, never use
steel wire in place of the nylon cutting
line.
STIHL PolyCut 6-3 Mowing Head with
Polymer Blades
For mowing unobstructed edges of
meadows (without posts, fences, trees
or similar obstacles).
It is important to follow the maintenance
instructions for the Polycut mowing
head.
Check the wear limit marks!
Wear limit marks are integrated in the
base of the PolyCut.
Do not continue using the PolyCut 6-3 if
one of the circular holes (1; arrow)
becomes visible or if the projecting rim
(2; arrow) has worn away. Install a new
mowing head.
WARNING
If the wear limit marks are ignored, there
is a risk of the cutting tool 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 in
one of the blades, always replace all the
blades.
8
FS 40, FS 40 C, FS 50, FS 50 C
Approved Combinations of Cutting Attachment, Deflector, Handle and Harness
0000-GXX-0401-A4
1
6
7
5
2
3
4
Cutting attachment Deflector Handle Carrying strap
English
Permissible combinations
Choose the correct combination from
the table depending on the cutting tool!
WARNING
For safety reasons no other
combinations are permitted – risk of
accidents!
Cutting attachments
Mowing heads
1 STIHL AutoCut C 6-2
2 STIHL DuroCut 5-2
3 STIHL PolyCut 7-3
4 STIHL PolyCut 6-2
Deflector
5 Guard with blade for mowing heads
Handle
6 Loop handle
Carrying strap
7 Shoulder strap can be used
FS 40, FS 40 C, FS 50, FS 50 C
9
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