Stihl 85 Manual

							
40 English / USAFS 80, FS 80 R, FS 85, FS 85 R
Rule of thumb
Turn high speed screw 
(H) about 
1/4  turn over for every 1000m 
(3.300 ft) change in altitude.
Conditions for adjustment
Adjust the high speed screw  (H) 
only if you are using a mowing head, 
making sure the cutting lines are full 
length (as far as the limiter blade on 
the deflector).
If you mount a metal cutting tool, 
use the standard setting.
: Carry out standard setting without 
changing position of high speed 
screw  (H).
: Warm up engine for about 5 minutes 
if you are using a metal cutting tool 
or about 3 minutes if you are using a 
mowing head.
: Open the throttle wide. At high altitude
:
Turn high speed screw  (H) clock-
wise (leaner) no further than stop 
until there is no noticeable increase 
in engine speed.
At sea level
: Turn high speed screw  (H) counter-
clockwise (richer) no further than 
stop until there is no noticeable 
increase in engine speed.
It is possible that maximum engine 
speed may be reached with the 
standard setting in each case.
Adjusting 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).
: Warm up the engine.
Engine stops while idling
: Turn idle speed screw  (LA) slowly 
clockwise until the engine runs 
smoothly – the cutting tool must not 
rotate. Cutting tool rotates when engine is 
idling
:
Turn idle speed screw  (LA) slowly 
counterclockwise until cutting tool 
stops rotating and then turn the 
screw about another 
1/2 to 1 turn in 
the same direction.
Erratic idling behavior, engine stops 
even though setting of LA screw is 
correct, poor acceleration Idle setting too lean:
: Turn low speed screw  (L) 
counterclockwise (about 
1/4 turn) 
until the engine runs and 
accelerates smoothly.
Erratic idling behavior Idle setting too rich:
: Turn low speed screw  (L) clockwise 
(about 
1/4  turn) until the engine runs 
and accelerates smoothly. 
						

							
41
FS 80, FS 80 R, FS 85, FS 85 R English / USA
If the engine is low on power, check the 
spark arresting screen in the muffler.
: Lift spark arresting screen and pull it 
out sideways.
: Clean spark arresting screen if 
necessary.
: If screen is damaged or coked up, fit 
a new one.
: Refit the spark arresting screen.
* see “Guide to Using this Manual” 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.If engine is down on power, difficult to 
start or runs poorly at idling speed, first 
check the spark plug.
:
Remove spark plug – see Starting / 
Stopping the Engine.
: Clean dirty spark plug.
: Check electrode gap  (A) and 
readjust if necessary – see 
Specifications.
: Use 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.
Fit a new spark plug after approx. 
100 operating hours  
or earlier if the electrodes are badly 
eroded.
Spark Arresting Screen* in 
Muffler
392BA035 KN
Checking the Spark Plug
000BA002 KN 
						

							
42 English / USAFS 80, FS 80 R, FS 85, FS 85 R
To reduce the risk of fire and burn 
injury, use only spark plugs 
authorized by STIHL. Always press 
spark plug boot 
(2) snugly onto 
spark plug terminal  (1) of the proper 
size. (Note: If terminal has 
detachable SAE adapter nut, it must 
be attached.) 
A loose connection between spark 
plug boot and ignition wire 
connector in the boot may create 
arcing that could ignite combustible 
fumes and cause a fire. :
Check grease level regularly - about 
every 25 hours of operation.
: Unscrew the filler plug  (1).
: If no grease can be seen on the 
inside of the filler plug, screw the 
tube  (2) of STIHL gear lubricant for 
brushcutters - see “Special 
Accessories” - into the filler hole.
: Squeeze up to 1/5 oz (5 g) grease 
into the gear housing.
Do not completely fill the gear 
housing with grease. 
: Refit the filler plug and tighten it 
down firmly.
Removing the Starter Cover
:Take out the screws ( 1).
: Lift the starter cover ( 2) away from 
the tank ( 3) and pull it out from 
under the shroud ( 4).
000BA036 TR
1
Lubricating the 
Gearbox
1
233BA010 KN
2
Replacing the Starter Rope 
and Rewind Spring
1
11
2
3
4
392BA013 KN 
						

							
43
FS 80, FS 80 R, FS 85, FS 85 R English / USA
Removing the Rope Rotor
:
Take out the screw ( 5).
: Remove the rope rotor very 
carefully.
The rewind spring is seated in the 
rope rotor and may pop out and 
uncoil if care is not taken. 
The pieces of broken spring may be 
under tension and fly apart 
unexpectedly when you remove the 
rope rotor. To help reduce the risk of 
injury, wear face protection and 
gloves.
Replacing the Starter Rope
:Use a screwdriver to pry the cap ( 6) 
out of the starter grip.
: Remove remaining rope from the 
rotor and grip, making sure the 
ElastoStart sleeve is not pushed out 
of the grip.
: Tie a simple overhand knot in the 
end of the new starter rope (see 
Specifications) and then thread the 
rope through the top of the grip and 
the rope bushing ( 7).
: Refit the cap in the grip. :
Pull the rope through the rotor and 
secure it with a simple overhand 
knot.
: Go to Installing the rope rotor.
Replacing a Broken Rewind 
Spring
Two types of replacement spring are 
available from the factory:
– A ready-to-fit rewind spring secured 
with a wire retainer.
– A rope rotor with pre-installed  rewind spring.
Installing the ready-to-fit rewind 
spring
: Lubricate the spring with a few 
drops of non-resinous oil – see 
Special Accessories – do not open 
the wire retainer!
5
392BA014 KN
6
7
392BA015 KN
392BA024 KN 
						

							
44 English / USAFS 80, FS 80 R, FS 85, FS 85 R
:
Carefully remove the parts of the old 
spring from the starter cover and 
rope rotor.
: Insert the new rewind spring in the 
rope rotor and, at the same time, 
engage the outer spring loop in the 
rotor’s recess – the wire retainer 
slips off in this process. 
If the spring pops out and uncoils, 
refit it in the counterclockwise 
direction, starting outside and 
working inwards.
: Go to Installing the Rope Rotor.
Installing rope rotor with rewind 
spring
: Carefully unpack the new rope rotor 
with rewind spring. The spring may 
pop out if not handled with care –
risk of injury.
: Lubricate the spring with a few 
drops of non-resinous oil – see 
Special Accessories.
: Go to Installing the Rope Rotor.
Installing the Rope Rotor
:Check dimension  a for inner spring 
anchor loop and bend it slightly if 
necessary.
: Coat rope rotor bearing bore with 
non-resinous oil – see Special 
Accessories.
: Slide the rotor onto the starter post – 
turn it back and forth until the rewind 
spring anchor loop ( 8) engages.
: Insert the screw ( 5) and tighten it 
down securely.
: Go to Tensioning the Rewind 
Spring.
Tensioning the Rewind Spring
:Make a loop in the unwound 
starter rope and use it to turn 
the rope rotor  six full revolutions 
counterclockwise. Hold the rotor 
steady – straighten the twisted rope 
– release the rotor – 
let go of rope slowly so that it winds 
onto the rotor.
: Check spring tension:
– The starter grip must be firmly  seated in the rope guide bushing. 
If the grip droops to one side: Add 
one more turn on rope rotor to 
increase spring tension.
– When the starter rope is fully  extended it must be possible to 
rotate the rotor another half turn. If 
this is not the case, the spring is 
overtensioned and  could break. 
Take one turn of rope off the rotor.
: Go to Fitting the Starter Cover.
a
389BA029 KN
a = 2mm
(0.08 in)
8
392BA025 KN
392BA044 KN 
						

							
45
FS 80, FS 80 R, FS 85, FS 85 R English / USA
Fitting the Starter Cover
:
Push the upper mounting boss ( 2) 
under the shroud ( 4) –
line up the tank ( 3)and push the 
lower part of cover onto the tank.
: Insert and tighten down the housing 
screws ( 1). For periods of about 3 months or longer
:
Drain and clean the fuel tank in a 
well ventilated area.
: Dispose fuel properly in accordance 
with local environmental 
requirements.
: Run engine until carburetor is dry – 
this helps prevent carburetor 
diaphragms sticking together.
: Remove, clean and inspect the 
cutting tool.
: Thoroughly clean the machine – pay 
special attention to the cylinder fins 
and air filter.
: Store the machine in a dry, high or 
locked location – out of the reach of 
children and other unauthorized 
persons. :
Use a file (special accessory) to 
sharpen cutting tools. In case of 
more serious wear or nicks: 
Resharpen with a grinder or have 
work done by STIHL dealer.
: Resharpen frequently, take away as 
little material as possible – two or 
three strokes of the file are usually 
enough. 
To avoid out-of-balance
: After resharpening about 5 times, 
have blade checked on STIHL 
balancer (special accessory) and 
rebalanced as necessary.
1
1 1
2
3 4
393BA045 KN
Storing the Machine Sharpening 
Metal Cutting Tools 
						

							
46 English / USAFS 80, FS 80 R, FS 85, FS 85 R
:
Resharpen the cutters  (1) uniformly 
– do not alter the contour of the 
parent blade  (2) in any way.
See cutting tool packaging for additional 
sharpening instructions.
22
1
2
11
002BA042 KN 
						

							
47
FS 80, FS 80 R, FS 85, FS 85 R English / USA
1) STIHL recommends that this work be done by a
   STIHL servicing dealer
*  Not in all versions, market-specific
Maintenance Chart
Please note that the following maintenance intervals apply for normal operating 
conditions. If your daily working time is longer than normal or cutting conditions 
are difficult (very dusty work area etc.), shorten the specified intervals accordingly.
before 
starting work
after finishing 
work or daily
after each
refueling stop
weekly
monthly
every 12 months
if problem
if damaged
as required
Complete machine Visual inspection (condition, leaks)
XX
Clean X
Control handle Check operation XX
Air filter Clean
XX
Replace X
Pick up body in fuel tank Check
X
Replace XXX
Fuel tank Clean XX
Carburetor Check idle adjustment – the cutting 
tool must not turn
XX
Readjust idle X
Spark plug Readjust electrode gap
X
Replace after about 100 operating 
hours
Cooling inlets Inspect
X
Clean X
Spark arresting screen* in muffler Check
XX
Replace XX
All accessible screws and nuts 
(not adjusting screws) Retighten
X
Anti-vibration element Check
X
Have replaced by servicing dealer
1)X 
						

							
48 English / USAFS 80, FS 80 R, FS 85, FS 85 R
Please note that the following maintenance intervals apply for normal operating 
conditions. If your daily working time is longer than normal or cutting conditions 
are difficult (very dusty work area etc.), shorten the specified intervals accordingly.
before 
starting work
after finishing 
work or daily
after each
refueling stop
weekly
monthly
every 12 months
if problem
if damaged
as required
Cutting toolsInspect
XX
Replace X
Check tightness  
of cutting tool XX
Metal cutting tools Sharpen XX
Gearbox lubrication Check
X
Replenish X
Safety labels Replace X 
						

							
49
FS 80, FS 80 R, FS 85, FS 85 R English / USA
   1 Fuel pump
   2 Choke lever
   3 Carburetor adjusting screws
   4 Starter grip
   5 Fuel filler cap
   6 Fuel tank
   7 Muffler
(with spark arresting screen*)
   8 Throttle trigger
   9 Slide control
10 Throttle trigger interlock
11 Bike handle
12 Handle support
13 Throttle cable retainer
14 Clamp 
(carrying ring for harness)
15 Spark plug boot
16 Air filter cover
17 Machine support
18 Barrier bar,
not in all versions, market-specific
19 Loop handle
20 Drive tube
# Serial number
Parts and Controls
Part 1
10 #
18 4
12 13
11
8
9
10
13 14 15
16
179 8
19
393BA043 KN
1
2
3
5 67
20
20
14