STIHL Fs 50 C Manual

							FS 40, FS 40 C, FS 50, FS 50 C
English
9 Important Adjustments
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.
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. 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.
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 attach-
ment should not move. For directions on 
how to adjust idle speed, see the appro-
priate section of your instruction 
manual.
Warning!
This unit is equipped with an ignition 
system that is normally in operational 
readiness. After the setting lever is used 
to stop the engine, it automatically 
springs back to the "on" position. If the 
engine is warm, it may be possible to 
start it by simply pulling the starter rope, 
with no further adjustments. To reduce 
the risk of injury, be particularly alert to 
keep children away from the unit.
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.
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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, over-
grown terrain. Watch for hidden 
obstacles such as tree stumps, roots 
and ditches to avoid stumbling. For bet-
ter footing, clear away scrub and 
cuttings. Be extremely cautious when 
working on slopes or uneven ground. 
						

							FS 40, FS 40 C, FS 50, FS 50 C
English
10Operating Instructions
In the event of an emergency, switch off 
the engine immediately – move the slide 
control / momentary stop switch to 0 or 
STOP.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. 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!
As soon as the engine is 
running, this product 
generates toxic exhaust 
fumes containing chemi-
cals, such as unburned 
hydrocarbons (including 
benzene) and carbon monoxide, that 
are known to cause respiratory prob-
lems, 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 inhal-
ing toxic fumes, never run the machine 
indoors or in poorly ventilated locations.
Warning!
If the vegetation being cut or the sur-
rounding 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. Sub-
stantial or repeated inhalation of dust 
and other airborne contaminants, in par-
ticular those with a smaller particle size, 
may cause respiratory or other ill-
nesses. Control dust at the source 
where possible. Use good work prac-
tices, 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 recom-
mendations of EPA/OSHA/NIOSH and 
occupational and trade associations 
with respect to dust ("particulate mat-
ter"). 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.
Warning!
Do not operate your power tool using 
the starting throttle lock, as you do not 
have control of the engine speed.Warning!
The rotating cutting attachment may 
fling foreign objects directly or by rico-
chet a great distance.
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.
15m (50ft) 
						

							FS 40, FS 40 C, FS 50, FS 50 C
English
11 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  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 prop-
erly 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 blade or head continues 
to loosen, see your STIHL dealer. Never 
use a trimmer with a loose cutting 
attachment.
Warning!
Replace a cracked, damaged or worn-
out head or a cracked, bent, warped, 
damaged, dull or worn out blade imme-
diately, 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 clean-
ing. Grass, weeds, etc. should be 
cleaned off the blade or from around the 
head at regular intervals.
Warning!
To reduce the risk of unintentional rota-
tion 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 oper-
ation. To reduce the risk of burn injury, 
do not touch the gear housing when it is 
hot.Warning!
Never modify your muffler. Any modifi-
cation 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 cyl-
inder housing or a damaged/deformed 
muffler shell may interfere with the cool-
ing 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 dam-
aged/deformed muffler shell. 
						

							FS 40, FS 40 C, FS 50, FS 50 C
English
12 (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.
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.Using the Mowing Heads
Do not use with mowing line longer than 
the intended length. With a properly 
mounted deflector, the built-in line-
limiting 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.
STIHL AutoCut mowing head
Nylon cutting cord advances 
automatically when tapped against the 
ground (TapAction).
STIHL PolyCut mowing head
Uses nonrigid, pivoting polymer blades. Warning!
S o m e  S T I H L  p o w e r  t o o l s  
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 proc-
ess, 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 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 combustible 
materials while it is still hot.
      
        
          
            
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							FS 40, FS 40 C, FS 50, FS 50 C
English
13 Do not continue using the PolyCut 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.
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.
Strictly follow the maintenance and 
repair instructions in the appropriate 
sections of your instruction manual. Warning!
If the wear limit marks are ignored, there 
is a risk of the cutting attachment shat-
tering 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.
1
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ual. 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 detach-
able 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 40, FS 40 C, FS 50, FS 50 C
English
14 In California, it is a violation of § 4442 or 
§ 4443 or 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.
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. Warning!
Do not operate your power tool if the 
muffler is damaged, missing or modi-
fied. An improperly maintained muffler 
will increase the risk of fire and hearing 
loss. Your muffler is equipped with a 
spark-arresting 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.
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. 
						

							FS 40, FS 40 C, FS 50, FS 50 C
English
15
Approved Combinations
The complete combination includes:
–Cutting attachment
–Deflector
–Handle
–Shoulder strap (special accessory 
only)
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
1STIHL AutoCut C 5-2
2STIHL AutoCut 5-2
3STIHL PolyCut 6-3
4STIHL FixCut 5-2Only mowing heads (1, 2, 3, 4) may be 
used on trimmers with a curved drive 
tube and loop handle.
Deflector
5Deflector with blade for mowing 
heads only (see "Mounting the 
Deflector").
Handle
6Loop handle
Harness
7Shoulder strap may be used
Approved Combinations of Cutting Attachment, Deflector, Handle and Harness
Cutting Attachment Deflector Handle Harness
546BA012 KN
12
67
5
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trol and contact with the cutting 
attachment.
Do not use rigid polymer blades, metal 
cutting attachments or circular saw 
blades on this unit.
Only mowing heads may be used on 
loop-handled trimmers with a curved 
drive tube. 
						

							FS 40, FS 40 C, FS 50, FS 50 C
English
16 Your new power tool comes with the 
loop handle mounted on the drive tube, 
but it must be turned and lined up to suit 
your requirements.
Adjusting the loop handle
Versions with screw (FS 40)
NUse a screwdriver or the 
combination wrench to loosen the 
screw (1) on the handle.
Versions with star knob (FS 50)
NLoosen the star knob (2) on the 
handle.
All versions
NTurn the handle to the vertical 
position.The loop handle can be adjusted to suit 
the height and reach of the operator and 
the application by changing 
distance (A).
Recommended distance (A): about 6 in 
(15 cm)
NSlide the handle to the required 
position.
NTighten down the screw or star knob 
so that the handle cannot be rotated 
on the drive tube.
NPush the deflector (1) over the 
clamp (2) as far as stop.
NInsert the nut (3) in the hex recess in 
the deflector – make sure the holes 
line up.
NInsert the screw (4) with washer and 
tighten it down firmly.
Mounting the Loop Handle
21
546BA003 KN
545BA004 KN
546BA004 KN
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2
232BA066 KN
4
546BA005 KN
3 
						

							FS 40, FS 40 C, FS 50, FS 50 C
English
17
Preparations
NLay your trimmer on sits back with 
the loop handle and shroud pointing 
down and the output shaft facing up.
Thrust Plate
The thrust plate is shipped with the 
PolyCut 6-3 and FixCut 5-2. It is only 
required for these mowing heads.STIHL AutoCut 5-2 mowing head, 
STIHL AutoCut C 5-2 mowing head
NPull the thrust plate (1), if fitted, off 
the shaft.
STIHL PolyCut 6-3 mowing head, 
STIHL FixCut 5-2 mowing head
NSlip the thrust plate (1) over the 
shaft (2) and engage hex recess (3) 
on the external hexagon (4).
Mounting the Mowing Head
Keep the instruction sheet for the 
mowing head in a safe place.STIHL AutoCut 5-2
NFit the spring (1) in the mowing 
head (2).
NWind the mowing line  (3) on to the 
spool (4).
NThread the nylon line through the 
sleeves and fit the spool in the head.
The individual steps are described in the 
instruction sheet supplied.
Mounting the Cutting 
Attachment
546BA006 KN
232BA033 KN
1
2 3
4
1
232BA054 KN
23 4
3 
						

							FS 40, FS 40 C, FS 50, FS 50 C
English
18 NSlip the mowing head (2) over the 
shaft (5) and engage hex recess (7) 
on the external hexagon (6).
NFit the cap (8) on the mowing head 
– screw it clockwise on to the shaft 
as far as stop and tighten it down 
firmly.STIHL AutoCut C 5-2
NSlip the mowing head (2) on to the 
shaft – as AutoCut 5-2.
NTurn the spool (9) clockwise until 
the two arrow heads line up – 
secure the spool in this position.
NInsert the cap (8) in the spool, press 
it down as far as stop and turn it 
clockwise at the same time.
NTurn the cap until you feel 
resistance and then tighten it down 
firmly by hand.STIHL PolyCut 6-3
NFit the thrust plate on the shaft.
NInsert the nut (10) in the mowing 
head.
NScrew the mowing head (11) 
clockwise on to the shaft (5) as far 
as stop.
NBlock the shaft – see "Blocking the 
Shaft".
NTighten down the mowing head.
Remove the locking pin.
7
5 2
232BA053 KN
68
9
681BA018 KN
Schnur/LINE  2
Schnur/LINE  128
11
5
681BA019 KN
10