STIHL Fs 40 C Owners Manual

FS 40, FS 40 C, FS 50, FS 50 C
English
19 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.
NOTICE
Fuel with an octane rating below 89 may 
increase engine temperatures. This, in 
turn, increases the risk of piston seizure 
and...

FS 40, FS 40 C, FS 50, FS 50 C
English
20 The machine‘s fuel tank should be 
cleaned as necessary.
Fuel mix ages
If not using MotoMix, only mix sufficient 
fuel for a few days of work, not to exceed 
30 days 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 
mix of oil and gasoline.
Dispose of empty mixing-oil containers 
only at authorized disposal locations....

FS 40, FS 40 C, FS 50, FS 50 C
English
21 NTurn the cap counterclockwise 
(approx. 1/4 turn).
NRemove fuel filler cap.
Refueling
Take care not to spill fuel while fueling 
and do not overfill the tank.
Closing the toolless filler cap
With grip in an upright position:NInsert the cap – positioning marks 
on the cap and the fuel tank opening 
must line up.
NThe cap should drop fully into the 
opening in this position.
NWhile pressing the cap down, twist it 
firmly clockwise as far as it will go 
(approx....

FS 40, FS 40 C, FS 50, FS 50 C
English
22 NTo correct a misalignment, turn the 
cap (with the grip up) until it drops 
fully into the tank opening.
NTwist 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.
NTwist the cap clockwise, closing it 
normally – see the sections 
"Closing" and "Checking for proper 
closure."
NIf your cap still does not tighten 
properly, it may be damaged or 
broken; immediately...

FS 40, FS 40 C, FS 50, FS 50 C
English
23
Starting the Engine
NPress the manual fuel pump 
bulb (4) at least five times – even if 
the bulb is filled with fuel.
Cold engine (cold start)
NPress in the choke lever (5) and turn 
it to g at the same time.
Warm engine (warm start)
NPress in the choke lever (5) and turn 
it to < at the same time.Also use this setting if the engine has 
been running but is still cold.
Cranking
NPlace the unit on the ground: It must 
rest securely on the engine support 
and the...

FS 40, FS 40 C, FS 50, FS 50 C
English
24 As soon as the engine runs
NPress down the throttle trigger 
lockout and open the throttle – the 
choke lever moves to the run 
positionF. After a cold start, warm 
up the engine by opening the 
throttle several times.
WARNING
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.
Stopping the Engine
NMove the stop switch in the direction 
of0  – the engine...

FS 40, FS 40 C, FS 50, FS 50 C
English
25 If there is a noticeable loss of engine 
power
NMove the choke lever (1) to 

FS 40, FS 40 C, FS 50, FS 50 C
English
26 The carburetor has been set at the 
factory to provide an optimum fuel-air 
mixture under most operating 
conditions.
Adjusting Idle Speed
Engine stops while idling
NWarm up the engine for about 
3 minutes.
NTurn the idle speed screw (LA) 
slowly clockwise until the engine 
runs smoothly – the cutting 
attachment must not run.
Cutting attachment runs when engine is 
idling
NTurn the idle speed screw (LA) 
counterclockwise until the cutting 
attachment stops...

FS 40, FS 40 C, FS 50, FS 50 C
English
27
WARNING
To reduce the risk of fire and burn injury, 
use only spark plugs authorized by 
STIHL. Always press the spark plug 
boot (1) snugly onto the spark plug 
terminal (2).
Do not use a spark plug with a 
detachable SAE adapter terminal (3). 
Arcing may occur that could ignite 
combustible fumes and cause a fire. 
This can result in serious injuries or 
damage to property. 
NOnly use resistor type spark plugs 
with solid, non-threaded terminals
Installing the...

FS 40, FS 40 C, FS 50, FS 50 C
English
28
Placing power tool on the ground
NSwitch off the engine.
NLay your trimmer on its back with 
the loop handle and shroud pointing 
down and the output shaft facing up.
Replacing Nylon Line
Always check the mowing head for signs 
of wear before replacing the nylon line.
WARNING
If there are signs of serious wear, 
replace the complete mowing head.
The nylon mowing line is referred to as 
"nylon line" or "line" in the following.
The mowing head is...