Instruction Manual
Table Of Contents
- STIHL FS 91, 91 R
- 1 Guide to Using this Manual
- 2 Safety Precautions and Working Techniques
- 2.1 Clothing and equipment
- 2.2 Transporting the machine
- 2.3 Refueling
- 2.4 Before starting
- 2.5 Starting the engine
- 2.6 Holding and guiding the machine
- 2.7 While working
- 2.8 Using mowing heads
- 2.9 When using metal cutting attachments
- 2.10 Vibrations
- 2.11 Maintenance and Repairs
- 2.12 Symbols on Deflectors
- 2.13 Shoulder Strap/Harness
- 2.14 Mowing Head with Nylon Line
- 2.15 STIHL Polycut Mowing Head with Polymer Blades
- 2.16 Risk of Kickout (Blade Thrust) with Metal Cutting Attachments
- 2.17 Grass Cutting Blade
- 2.18 Brush Knife
- 2.19 Circular Saw Blade
- 3 Approved Combinations of Cutting Attachment, Deflector, Handle and Harness
- 4 Approved Power Tool Attachments
- 5 Mounting the Bike Handle
- 6 Mounting the Loop Handle
- 7 Adjusting the Throttle Cable
- 8 Fitting the Carrying Ring
- 9 Mounting the deflector
- 10 Mounting the Cutting Attachment
- 10.1 Placing power tool on the ground
- 10.2 Mounting Hardware for Cutting Attachments
- 10.3 Blocking the Shaft
- 10.4 Removing the Mounting Hardware
- 10.5 Mounting the Cutting Attachment
- 10.6 Fitting Mowing Head with Screw Mounting
- 10.7 Remove the mowing head.
- 10.8 Mounting Metal Cutting Attachments
- 10.9 Removing the Metal Cutting Attachment
- 11 Fuel
- 12 Fueling
- 13 Fitting the Harness
- 14 Balancing the Machine
- 15 Starting / Stopping the Engine
- 16 Transporting the Unit
- 17 Operating Instructions
- 18 Replacing the Air Filter
- 19 Adjusting the Carburetor
- 20 Spark Arresting Screen in Muffler
- 21 Spark Plug
- 22 Engine Running Behavior
- 23 Lubricating the Gearbox
- 24 Storing the Machine
- 25 Sharpening Metal Cutting Blades
- 26 Maintaining the Mowing Head
- 27 Maintenance and Care
- 28 Minimize Wear and Avoid Damage
- 29 Main Parts
- 30 Specifications
- 31 Maintenance and Repairs
- 32 Disposal
- 33 EC Declaration of Conformity
► Fit a new spark plug after about 100 operating
hours – or sooner if the electrodes are badly
eroded. Install only suppressed spark plugs of
the type approved by STIHL – see "Specifica‐
tions".
21.1 Removing the Spark Plug
3
2
1
0000-GXX 0537-A0
► Remove the cover (1).
► Pull off the spark plug boot (2).
► Unscrew the spark plug (3).
21.2 Checking the Spark Plug
000BA039 KN
A
► Clean dirty spark plug.
► Check electrode gap (A) and readjust if neces‐
sary – see "Specifications".
► Rectify the problems which have caused foul‐
ing of the spark plug.
Possible causes are:
–
Too much oil in fuel mix.
–
Dirty air filter.
–
Unfavorable running conditions.
1
000BA045 KN
WARNING
Arcing may occur if the adapter nut (1) is loose
or missing. Working in an easily combustible or
explosive atmosphere may cause a fire or an
explosion. This can result result in serious inju‐
ries or damage to property.
► Use resistor type spark plugs with a properly
tightened adapter nut.
21.3 Installing the Spark Plug
► Screw the spark plug (3) into the cylinder.
► Tighten down the spark plug (3) with the com‐
bination wrench.
► Press the boot (2) firmly onto the spark plug.
► Fit the cover (1) and screw it down firmly.
22 Engine Running Behavior
If engine running behavior is unsatisfactory even
though the air filter is clean and the carburetor is
properly adjusted, the cause may be the muffler.
Have the muffler checked for contamination (car‐
bonization) by your servicing dealer.
STIHL recommends that you have servicing and
repair work carried out exclusively by an author‐
ized STIHL servicing dealer.
23 Lubricating the Gearbox
1
0000-GXX-0536-A0
Check grease level after every 25 hours of oper‐
ation and re-lubricate if necessary.
► Remove the screw plug (1).
► If no grease can be seen on the inside of the
screw plug (1): Screw the tube (2) of STIHL
gear lubricant (special accessory) into the filler
hole.
► Squeeze no more than 5 g (1/5 oz) grease into
the gearbox.
NOTICE
Do not completely fill the gearbox with grease.
► Unscrew the tube (2).
English 22 Engine Running Behavior
32 0458-426-8321-B