Stihl Fs 45 C Manual

							FS 45, FS 46
English
19 Block the drive shaft.
NTo block the shaft, insert a suitable 
tool (12) through the holes (13) in 
the deflector and thrust plate – turn 
the thrust plate back and forth if 
necessary.STIHL FixCut 5-2
NSlip the thrust plate (2) over the 
shaft.
NPlace the mowing head on the 
thrust plate (2).
Collar (see arrow) must engage the 
mowing head's mounting hole.
NPush the thrust washer (3) over the 
shaft (1) so it is seated on the base.
NBlock the shaft – see "Blocking the 
Shaft".
NUse the combination wrench (5) 
(special accessory) to screw the 
mounting nut (4) on to the output 
shaft and tighten it down firmly.
Remove the locking pin.
Removing the mowing head
STIHL AutoCut
NHold the mowing head steady.
NUnscrew the cap counterclockwise.
STIHL PolyCut
NBlock the shaft – see "Blocking the 
Shaft".
NUnscrew the mowing head 
counterclockwise.
STIHL FixCut
NBlock the shaft – see "Blocking the 
Shaft".
NUse the combination wrench 
(special accessory) to loosen and 
unscrew the mounting nut 
counterclockwise from the output 
shaft.
If the mounting nut turns too freely, fit a 
new one.
3
1
2 4
232BA074 KN
5 
						

							FS 45, FS 46
English
20
Adjusting Nylon Line
STIHL AutoCut
NHold the rotating mowing head 
above the ground – tap it on the 
ground once – about 1.2 in. (3 cm) 
fresh line is advanced.
NThe blade (1) on the deflector (2) 
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 
h a v e  a  m i n i m u m  l e n g t h  o f   1 in. (2.5 cm).
If the mowing line is shorter than 1 in. 
(2.5 cm):
To reduce the risk of injury, always shut 
off the engine before adjusting the 
mowing line by hand.NTurn the trimmer on its back.
NPress down the cap on the spool as 
far as stop.
NPull the ends of the lines out of the 
spool.
If the spool is empty, see "Replacing 
Nylon Line".
All other mowing heads
Refer to the instructions supplied with 
the mowing head.
To reduce the risk of injury, always shut 
off the engine before adjusting the 
mowing line by hand.
Replacing Nylon Line / Polymer Blades 
STIHL AutoCut
See chapter on "Replacing Nylon Line".
STIHL PolyCut, FixCut
Refer to the instructions supplied with 
the mowing head.This engine is certified to operate on 
unleaded gasoline and the STIHL two-
stroke engine oil at a mix ratio of 50:1.
Your engine requires a mixture of high-
quality 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.
1
232BA007 KN
2
)XHO 
						

							FS 45, FS 46
English
21 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.
W e  r e c o m m e n d  S T I H L  H P  U l t r a  2 - C y c l e  
Engine Oil since it is specially 
formulated for use in STIHL engines.
Do not use BIA or TCW rated (two-
stroke 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 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.
Dispose of empty mixing-oil containers 
only at authorized disposal locations.Before fueling, clean the filler cap and 
the area around it to ensure that no dirt 
falls into the tank.
Always thoroughly shake the mixture in 
the canister before fueling your 
machine.
In order to reduce the risk of fire and 
personal injury from escaping gas vapor 
and fumes, remove the fuel filler cap 
carefully so as to allow any pressure 
build-up in the tank to release slowly.
After fueling, tighten fuel cap as securely 
as possible by hand. 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.
Gaso-
lineOil (STIHL 50:1 or equiva-
lent high-quality oils)
US gal. US fl.oz.
12.6
2 1/2 6.4
5 12.8
Fueling
232BA046 KN 
						

							FS 45, FS 46
English
22
Controls
1Stop switch
2Throttle trigger lockout
3Throttle trigger
4Tongue of throttle trigger
5Catch
Positions of stop switch
6I – normal run position – the engine 
is running or can start
70 – Stop – engine off – the ignition is 
switched off
Starting
NMove the stop switch to I.
NPress down the throttle trigger 
interlock and hold it there.
NSqueeze the throttle trigger until the 
catch on the tongue (4) can be 
engaged on the housing (arrow).
NNow release the throttle trigger, 
tongue and trigger interlock in that 
order. This is the starting throttle 
position.NSet the choke lever (8) to
NPress the fuel pump bulb (9) at least 
five times – even if the bulb is 
already filled with fuel.Starting / Stopping the 
Engine
2
232BA080 KN
167
54
3233BA047 KN
4
gif the engine is cold
efor warm start – also use this posi-
tion if the engine has been running 
but is still cold.
9
8
232BA011 KN 
						

							FS 45, FS 46
English
23 Starting
NPlace 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 of any other obstacles.
NMake sure you have a safe and 
secure footing.
NHold 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.NHold the starter grip with your right 
hand.
NPull 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.
NDo not let the starter grip snap back. 
Guide it slowly back into the housing 
so that the starter rope can rewind 
properly.
NContinue cranking.When the engine begins to fire:
NAfter no more than five pulls, move 
the choke lever (8) to e.
NContinue cranking.
As soon as the engine runs
NSqueeze the throttle trigger to 
disengage the tongue – the engine 
will settle down to idle speed.
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.
Shut off the engine.
NMove the stop switch to0. 
If the engine does not start
Choke lever
If you did not move the choke lever to e 
quickly enough after the engine began to 
fire, the combustion chamber is flooded.
232BA012 KN
232TI013 KN
232BA014 KN
8
232TI015 KN 
						

							FS 45, FS 46
English
24 NSet the choke lever to e .
NMove the stop switch to I, interlock 
lever and throttle trigger to the 
starting throttle position.
NStart the engine by pulling the 
starter rope briskly – 10 to 20 pulls 
may be necessary. 
If the engine still does not start
NMove the stop switch to 0.
NRemove the spark plug – see 
"Spark Plug".
NDry the spark plug.
NCrank the engine several times with 
the starter to clear the combustion 
chamber.
NRefit the spark plug – see "Spark 
Plug".
NMove the stop switch to I.
NSet the choke lever to e – even if 
the engine is cold.
NNow start the engine.
Fuel tank run until completely dry
NAfter refueling, press the fuel pump 
bulb at least five times – even if the 
bulb is filled with fuel.
NSet the choke lever to suit the 
engine temperature.
NStart the engine.
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 engine-
mounted 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-of-
service periods – see "Storing the 
Machine".If there is a noticeable loss of engine 
power
NSet the choke lever to g.
NPress in the tab (1) and swing the 
filter cover (2) down. 
NClean away loose dirt from around 
the filter.
Operating InstructionsCleaning the Air Filter
232BA017 KN
12 
						

							FS 45, FS 46
English
25 NRemove the felt element (3) from 
the filter housing (4) and replace it – 
knock out or blow out as a 
temporary measure – do not wash.
NReplace damaged parts.
NFit the felt element (3) in the filter 
housing (4).
NClose the filter cover so that it snaps 
into position.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.
General Information
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 screw within fine 
limits.
Standard Setting
NStopping the Engine
NMount the cutting attachment.
NCheck the air filter and replace it if 
necessary.
NHave the spark arresting screen 
(not all markets) checked – see 
“Inspection and Maintenance by 
Dealer"
232BA018 KN
4
3
(QJLQH0DQDJHPHQW$GMXVWLQJWKH&DUEXUHWRU 
						

							FS 45, FS 46
English
26 NTurn high speed screw (H) 
counterclockwise as far as stop (no 
more than 3/4 turn).
NTurn the low speed screw (L) 
carefully clockwise as far as stop, 
then turn it back 1.5 turns.
NStart and warm up the engine if 
necessary.
NAdjust idle speed with the idle speed 
screw (LA) so that the cutting 
attachment does not rotate.
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 or at sea level.Rule of thumb:
Turn the high speed screw (H) about 
one quarter of a turn for every 1000 m 
(3300 ft) change in altitude.
Conditions for adjustment
If a nylon line mowing head is used, 
make sure the lines reach as far as the 
limiter blade on the deflector.
NCarry out the standard setting 
without disturbing the high speed 
screw (H).
NWarm up the engine for about 3 
minutes.
NOpen the throttle wide.
At high altitude
NTurn the high speed screw (H) 
clockwise (leaner), no further than 
stop, until there is no further 
noticeable increase in engine 
speed.
At sea level
NTurn 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.
Aadjusting Idle Speed
It is usually necessary to change the 
setting of the idle speed screw (LA) after 
every correction to the low speed 
screw (L).NWarm up the engine.
Engine stops while idling
NTurn the idle speed screw (LA) 
slowly clockwise until the engine 
runs smoothly – the cutting 
attachment must not turn.
Cutting attachment rotates when engine 
is idling
NTurn the idle speed screw (LA) 
counterclockwise until the cutting 
attachment stops moving and then 
rotate the screw another 1/2 to 1 
turn in the same direction.
If the cutting attachment continues to run 
when the engine is idling, have your 
machine checked and repaired by your 
servicing dealer.
Erratic idling behavior, engine stops 
even though setting of LA-screw has 
been corrected, poor acceleration
Idle setting is too lean:
NIdle setting is too lean: Rotate the 
low speed screw (L) about 1/4 turn 
counterclockwise until the engine 
runs and accelerates smoothly.
Erratic idling behavior 
Idle setting is too rich
NRotate the low speed screw (L) 
about 1/4 turn clockwise until the 
engine runs and accelerates 
smoothly.
LH
LA
233BA050 KN 
						

							FS 45, FS 46
English
27 If engine is down on power, difficult to 
start or runs poorly at idling speed, first 
check the spark plug.
Fit a new spark plug after approx. 100 
operating hours or earlier if the 
electrodes are badly eroded.
Wrong fuel mix (too much engine oil in 
the gasoline), a dirty air filter and 
unfavorable running conditions (mostly 
at part throttle etc.) affect the condition 
of the spark plug. These factors cause 
deposits to form on the insulator nose 
which may result in trouble in operation.
Removing the Spark Plug
NMove the stop switch to0.
NPull off the spark plug boot (1).
NUnscrew the spark plug.
Checking the Spark Plug
NClean dirty spark plug.
NCheck electrode gap (A) and 
readjust if necessary – see 
"Specifications".
NUse only resistor type spark plugs of 
the approved range.
Rectify problems which have caused 
fouling of spark plug:
–Too much oil in fuel mix.
–Dirty air filter.
–Unfavorable running conditions, 
e.g. operating at part load.
Installing the spark plug
NScrew home the spark plug, fit the 
boot and press it down firmly.
Spark Plug
1
232BA081 KN
000BA039 KNA
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nector in the boot may create arcing that 
could ignite combustible fumes and 
cause a fire.
1
2
000BA071 KN 
						

							FS 45, FS 46
English
28 To help prolong the wear life of the 
starter rope, observe the following 
points:
NPull the starter rope only in the 
direction specified.
NDo not pull the rope over the edge of 
the guide bushing.
NDo not pull out the rope more than 
specified.
NDo not allow the starter grip to snap 
back, guide it back into the housing 
slowly – see chapter on "Starting / 
Stopping the Engine."
Have a damaged starter rope replaced 
by your dealer before it breaks 
completely. STIHL recommends that 
you have servicing and repair work 
carried out exclusively by an authorized 
STIHL servicing dealer.For periods of 3 months or longer
NDrain and clean the fuel tank in a 
well ventilated area.
NDispose of fuel properly in 
accordance with local 
environmental requirements.
NRun the engine until the carburetor 
is dry – this helps prevent the 
carburetor diaphragms sticking 
together.
NRemove, clean and inspect the 
cutting attachment.
NThoroughly clean the machine – pay 
special attention to the cylinder fins 
and air filter.
NStore the machine in a dry and 
secure location – out of the reach of 
children and other unauthorized 
persons.
STIHL AutoCut C 5-2
Always check the mowing head for signs 
of wear before replacing the nylon line.
If there are signs of serious wear, 
replace the complete mowing head.
Preparations
NShut off the engine.
NPut the machine on the ground with 
the mowing head facing up.
Disassembling the mowing head and 
removing remaining nylon line
In normal operation, the supply of nylon 
line in the head is used up completely.
Rewind StarterStoring the MachineReplacing Nylon Line