Stihl Hs 81 R Manual

							HS 81 R, HS 81 RC, HS 81 T, HS 81 TCEnglish
9 Operating Instructions
In the event of an emergency, switch off 
the engine immediately – move the slide 
control / stop switch to 0 or STOP.Accelerating the engine while the blades 
are blocked increases the load and will 
cause the clutch to slip continuously. 
This may result in overheating and 
damage to important components (e.g. 
clutch, polymer housing components) – 
which can then increase the risk of injury 
from the blades moving while the engine 
is idling.
Take particular care when cutting 
hedges next to or against wire fences. 
Do not touch the wire with the cutting 
blades. When working close to the 
ground, make sure that no sand, grit or 
stones get between the cutter blades.
Striking solid foreign objects such as 
stones, fence wire or metal could 
damage the cutting attachment and may 
cause blades to crack, chip or break. 
STIHL does not recommend the use of 
your power tool when cutting in areas 
where the blades could contact such 
objects.Check the cutting blades at regular short 
intervals during operation, or 
immediately if there is a noticeable 
change in cutting behavior:
–Shut off the engine.
–Wait until the cutting blades have 
come to a complete standstill.
–Check condition and tightness, look 
for cracks.
–Check sharpness.
–Replace damaged or dull cutting 
tools immediately, even if they have 
only superficial cracks. 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 associa-
tions with respect to dust (particulate 
matter.) When the inhalation of dust 
cannot be substantially controlled, i.e., 
kept at or near the ambient (back-
ground) 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 cutter blades continue to move for a 
short period after the throttle trigger is 
released (flywheel effect.)
Warning!
Before you start work, examine the 
hedge area for stones, fence wire, metal 
or other solid objects which could dam-
age the cutter blades.
Warning!
Observe the cutting blades at all times – 
do not cut any areas of the hedge that 
you cannot see. When cutting the top of 
a taller hedge, check the other side of 
the hedge frequently for bystanders, 
animals and obstructions.
Danger!
Your power tool is not 
insulated against electric 
shock. To reduce the risk 
of electrocution, never 
operate this power tool in 
the vicinity of any wires or 
cables (power, etc.) which may be car-
rying electric current.
Warning!
If the cutting tool becomes clogged or 
stuck, always turn off the engine and 
make sure the cutting tool has stopped 
before cleaning. Grass, weeds, etc. 
should be cleaned off the cutting tool at 
regular intervals.
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. 
						

							HS 81 R, HS 81 RC, HS 81 T, HS 81 TC English
10 After Finishing Work
Always clean dust and dirt off the 
machine – do not use any grease 
solvents for this purpose.
Spray the blades with STIHL resin 
solvent. Start and run the engine briefly 
so that the solvent is evenly distributed.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 
section of your instruction manual. 
Please refer to the maintenance chart in 
this manual.
Wear gloves when handling or 
performing maintenance on blades. 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.
Warning!
To reduce the risk of fire and burn injury, 
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 (e.g. the trunk of a felled tree) 
away from any combustible substances.
Warning!
Never modify your muffler. The muffler 
could be damaged and cause an 
increase in heat radiation or sparks, 
thereby increasing the risk of fire and 
burn injury. You may also permanently 
damage the engine. Have your muffler 
serviced and repaired by your STIHL 
servicing dealer only.
Warning!
Use only identical STIHL replacement 
parts for maintenance and repair. Use of 
non-STIHL parts may cause serious or 
fatal injury.
Warning!
Always stop the engine and make sure 
that the cutting tool is stopped before 
doing any maintenance or repair work or 
cleaning the power tool. Do not attempt 
any maintenance or repair work not 
described in your instruction manual. 
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 spark plug boot snugly onto spark 
plug terminal of the proper size. (Note: If 
terminal has detachable SAE adapter 
nut, it must be securely attached.) A 
loose connection between spark plug 
terminal 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 
ignition wire boot removed from the 
spark plug or with a removed spark 
plug, since uncontained sparking may 
cause a fire.
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. If your muffler was equipped with a 
spark-arresting screen to reduce the 
risk of fire, never operate your power 
tool if the screen is missing or damaged. 
Remember that the risk of forest fires is 
greater in hot or dry weather.
Warning!
Never repair damaged cutting attach-
ments by welding, straightening or mod-
ifying the shape. This may cause parts 
of the cutting tool to come off and result 
in serious or fatal injuries. 
						

							HS 81 R, HS 81 RC, HS 81 T, HS 81 TCEnglish
11 Keep the cutting tool sharp. 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 this 
manual.
HS 81 R
The HS 81 R is designed for cutting 
hedges and shrubs with thicker stems 
and branches.
HS 81 T
The HS 81 T is designed for shaping 
and trimming hedges and shrubs with 
thinner branches.
Use the HS 81 R hedge trimmer for 
cutting hedges with thicker branches.
Cutting Season
Observe country-specific or municipal 
rules and regulations for cutting hedges.Do not use your power tool during other 
peoples rest periods.
Cutting Sequence
Use lopping shears or a chain saw to cut 
out thick branches first.
Cut both sides of the hedge first, then 
the top.
Disposal
Do not throw cuttings in the garbage can 
– they can be composted!
Using the Unit 
						

							HS 81 R, HS 81 RC, HS 81 T, HS 81 TC English
12
Working Technique
Vertical Cut
Swing the cutting blade from the bottom 
upwards in an arc – lower the nose of the 
blade, move along the hedge and then 
swing the blade up again in an arc.
Any working position above head height 
is tiring. To minimize the risk of 
accidents, work in such positions for 
short periods only.Horizontal Cut
Hold the cutter bar at an angle of 0° to 
10° as you swing the hedge trimmer 
horizontally.
Swing the cutting blade in an arc 
towards the outside of the hedge so that 
the cuttings are swept to the ground.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.Fuel 
						

							HS 81 R, HS 81 RC, HS 81 T, HS 81 TCEnglish
13 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.
We recommend STIHL HP Ultra 2-Cycle 
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.
Preparations
NBefore fueling, clean the filler cap 
and the area around it to ensure that 
no dirt falls into the tank.
NPosition the machine so that the 
filler cap is facing up.
NAlways thoroughly shake the 
mixture in the canister before 
fueling your machine. 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
In order to reduce the risk of burns 
or other 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. 
						

							HS 81 R, HS 81 RC, HS 81 T, HS 81 TC English
14
Opening the cap
NSwing the grip 90° to the upright 
position.
NTurn the cap counterclockwise
(about a quarter turn).
NRemove the filler cap.
Fueling
Take care not to spill fuel while fueling 
and do not overfill the tank.
Closing the cap
NInsert the cap in the opening – with 
the grip upright – the marks must 
line up.
NTurn cap clockwise as far as stop 
(about a quarter turn).
NFold the grip down so that it is flush 
with the top of the cap.
If the grip does not lie completely flush 
with the cap and the lug on the grip does 
not engage the recess in the filler neck 
(arrow), the cap is not properly seated 
and tightened and you must repeat the 
above steps.Change the fuel pickup body
Change the fuel pickup body once every 
year.
NDrain the fuel tank.
NUse a hook to pull the fuel pickup 
body out of the tank and take it off 
the hose.
NPush the new pickup body into the 
hose.
NPlace the pickup body in the tank.
Do not kink the fuel hose – do not 
use any sharp or pointed tools. 
						

							HS 81 R, HS 81 RC, HS 81 T, HS 81 TCEnglish
15 The rear handle can be turned through 
90° to the left or right for better control 
and comfort in all cutting situations.
NLet go of the throttle trigger. Do not 
open the throttle.
NRelease the lock (1).
NTurn the handle (2) to the required 
position and re-engage the lock (1).
The throttle trigger may be used again 
when the handle is locked in position.
Do not operate the throttle while the 
handle lock is released. Never release 
the lock while you are operating the 
throttle.NObserve safety precautions – see 
chapter on Safety Precautions and 
Working Techniques.
NMove the stop switch (1) to I.
NPress down the throttle lockout (2) 
and squeeze the throttle trigger (3) 
at the same time – hold both levers 
in that position.
NPress in the starting throttle 
button (4). 
NLet go of the lockout lever, throttle 
trigger and starting throttle button. 
This is the starting throttle position.
NSet the choke lever (5) toNPress the fuel pump bulb at least 
five times – even if the bulb is filled 
with fuel.
Starting
NPlace the unit on the ground.
NRemove the blade scabbard. Check 
that the cutting blades are not 
touching the ground or any other 
obstacles.
NMake sure you have a safe and 
secure footing.
NHold the unit firmly with your left 
hand on the fan housing and press 
down.
NHold the starter grip with your right 
hand.
Rear HandleStarting / Stopping the 
Engine
gif the engine is cold
efor warm start – also use this posi-
tion if the engine has been running 
but is still cold.
443BA038 KN
443BA039 KN 
						

							HS 81 R, HS 81 RC, HS 81 T, HS 81 TC English
16 Version without Easy2Start
NPull the starter grip slowly until you 
feel it engage and then give it a brisk 
strong pull.
NDo not let the starter grip snap back. 
Guide it slowly back into the housing 
so that the starter rope can rewind 
properly.
Version with Easy2Start
NPull the starter grip steadily.
When the engine begins to fire:
NMove the choke lever to e and 
continue cranking.
As soon as the engine runs
NOpen the throttle wide – the starting 
throttle button pops out and the 
engine can settle down to idle 
speed.
Stopping the engine
NMove the stop switch to0.
Other hints on starting
At very low outside temperatures – 
warm up the engine
As soon as the engine runs:
NAllow engine to run in starting 
throttle position for about 10 
seconds.
NOpen the throttle wide – the starting 
throttle button pops out and the 
engine can settle down to idle 
speed.
If the engine does not start
If you did not turn the choke lever to e 
quickly enough after the engine began to 
fire, the combustion chamber is flooded.
NSet the choke lever to e – even if 
the engine is cold.
NNow start the engine with a few 
brisk pulls of the starter rope.
If fuel tank has been run completely 
dry and then refueled
NPress the fuel pump bulb at least 
five times – even if the bulb is filled 
with fuel.
NNow start the engine.The unit is equipped with either a felt or 
paper filter element.
If there is a noticeable loss of engine 
power
Felt filter
NTurn the choke lever to g
NTake out the screw (1).
NRemove the filter cover (2).
NClean away loose dirt from around 
the filter.
NRemove the filter element (3).
NFit a new filter element. As a 
temporary measure you can knock it 
out on the palm of your hand or blow 
it out with compressed air. Do not 
wash.
NInstall the filter element.
NFit the filter cover.
NInsert the screw and tighten it down 
firmly.
Do not pull out the starter rope all 
the way – it might otherwise 
break.
Cleaning the Air Filter
1
443BA040 KN
2 
						

							HS 81 R, HS 81 RC, HS 81 T, HS 81 TCEnglish
17 Paper filter
NTurn the choke lever to g
NTake out the screw (1).
NRemove the filter cover (2).
NClean away loose dirt from around 
the filter and inside the filter cover.
NRemove and check the filter 
element (3) – replace if dirty or 
damaged.
NFit the filter in the filter housing.NPosition filter cover against the left 
side of the filter housing and swing it 
to the right – the two lugs (arrows) 
must engage the filter cover 
openings. 
NInsert the screw and tighten it down 
firmly.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.
1
443BA034 KN
2
443BA035 KN3
443BA036 KN
Engine Management 
						

							HS 81 R, HS 81 RC, HS 81 T, HS 81 TC English
18
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
NCheck the air filter and clean or 
replace if necessary.
NCheck the spark arresting screen 
(country-specific) in the muffler and 
clean or replace if necessary.
NTurn high speed screw (H) 
counterclockwise as far as stop (no 
more than 3/4 turn).NCarefully turn the low speed 
screw (L) down onto its seat 
(clockwise).
NOpen the low speed screw (L) one 
full turn.
Readjust idle
Engine stops while idling
NCheck the standard setting. 
NTurn the idle speed screw (LA) 
clockwise until the cutting blades 
begin to run – then back it off 
2 1/2 turns.
Cutting blades run when engine is 
idling
NCheck the standard setting. 
NTurn the idle speed screw (LA) 
counterclockwise until the cutting 
blades stop moving –  then turn it 
another 2 1/2 turns in the same 
direction.
Erratic idling behavior, poor 
acceleration
NCheck the standard setting. 
NIdle setting is too lean: Rotate the 
low speed screw (L) about 1/4 turn 
counterclockwise until the engine 
runs and accelerates smoothly.
Machine stops when it is swung at 
idle speed
NCheck the standard setting. 
NIdle setting is too lean: Rotate the 
low speed screw (L) about 1/4 turn 
counterclockwise until the engine 
idles smoothly.It is usually necessary to change the 
setting of the idle speed screw (LA) after 
every correction to the low speed 
screw (L).
Fine Tuning for Operation in Mountains or at Sea Level
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.
NCheck the standard setting.
NWarm up the engine.
NAdjust idle speed properly.
At high altitude
NTurn high speed screw (H) 
clockwise (leaner) – no further than 
stop.
At sea level
NTurn high speed screw (H) slightly 
counterclockwise (richer) – no 
further than stop.
Adjusting the Carburetor
LH
LA443BA037 KN
If the setting is too lean there is a 
risk of engine damage due to 
insufficient lubrication and 
overheating.