STIHL HL 90 Owner's Manual
STIHL HL 90
STIH)
Instruction Manual
Manual de instrucciones
Warning!
Read and follow all safety precautions in
Instruction Manual – improper use can cause
serious or fatal injury.
Advertencia!
Lea y siga todas las precauciones de
seguridad dadas en el manual de
instrucciones – el uso incorrecto puede
causar lesiones graves o mortales.
Contents
English / USA
Guide to Using this Manual .............. 2
Safety Precautions and
Working Techniques ......................... 3
Using the Hedge Trimmer .............. 13
Mounting the Gearbox .................... 14
Adjusting the Throttle Cable ........... 15
4-MIX Engine .................................. 16
BA_SE_212_003_01_03.fmPrinted on chlorine-free paper.
Fuel ................................................ 16
Fueling ............................................ 17
Starting / Stopping
the Engine ...................................... 18
Operating Instructions .................... 21
Cleaning the Air Filter ..................... 21
Motor Management ........................ 21
Adjusting the Carburetor ................ 22
Spark Arresting Screen in Muffler ... 23
Checking the Spark Plug ................ 24
Lubricating the Gearbox ................. 25
Replacing Starter Rope
and Rewind Spring ......................... 26
Storing the Machine ........................ 29
Sharpening Instructions .................. 29
Inspections and Maintenance
by Dealer ........................................ 29
Maintenance Chart ......................... 30
Main Parts and Controls ................. 32
Printing inks contain vegetable oils; paper can be recycled.
Specifications ................................. 34
Special Accessories ....................... 35
Maintenance and Repairs ............... 35
STIHL Incorporated
Federal Emission Control
Warranty Statement ........................ 36
STIHL Incorporated California
Exhaust and Evaporative Emissions
Control Warranty Statement ........... 38
Trademarks .................................... 40
Allow only persons who understand this
manual to operate your hedge cutter.
To receive maximum performance and
satisfaction from your STIHL hedge
cutter, it is important that you read and
understand the maintenance and safety
precautions, starting on page 3, before
using your hedge cutter.
Contact your STIHL dealer or the STIHL
distributor for your area if you do not
understand any of the instructions in this
manual.
!Warning!
Because a hedge cutter is a high-speed
cutting tool some special safety
precautions must be observed to reduce
the risk of personal injury.
Careless or improper use may cause
serious or even fatal injury.
STIHL's philosophy is to continually
improve all of its products. As a result,
engineering changes and improvements are made from time to time. If the
operating characteristics or the
appearance of your hedge cutter differs
from those described in this manual,
please contact your STIHL dealer for
information and assistance.
STIHl
© ANDREAS STIHL AG & Co. KG, 2008
0458 445 8621 A. M1. C8. PM. Printed in USA
1HL 90 K
English / USA
Guide to Using this Manual
Pictograms
All the pictograms attached to the
machine are shown and explained in
this manual.
The operating and handling instructions
are supported by illustrations.
Symbols in text
The individual steps or procedures
described in the manual may be marked
in different ways:
: A bullet marks a step or procedure
without direct reference to an
illustration.
A description of a step or procedure that
refers directly to an illustration may
contain item numbers that appear in the
illustration.
Example:
Loosen the screw (1)
Lever (2) ...
In addition to the operating instructions,
this manual may contain paragraphs
that require your special attention. Such
paragraphs are marked with the
symbols described below:
Warning where there is a risk of an
accident or personal injury or
serious damage to property.
Caution where there is a risk of
damaging the machine or its
individual components.
Note or hint which is not essential
for using the machine, but may
improve the operator’s understanding of the situation and result
in better use of the machine.
Note or hint on correct procedure in
order to avoid damage to the
environment.
Equipment and features
This instruction manual may refer to
several models with different
features. Components that are not
installed on all models and related
applications are marked with an
asterisk (*). Such components may
be available as special accessories
from your STIHL dealer.
Engineering improvements
STIHL’s philosophy is to continually
improve all of its products. As a result,
engineering changes and improvements
are made from time to time. If the
operating characteristics or the
appearance of your machine differ from
those described in this manual, please
contact your STIHL dealer for
assistance.
Therefore some changes, modifications
and improvements may not be covered
in this manual.
2
HL 90 K
Safety Precautions and
Working Techniques
English / USA
Because a hedge trimmer
is a high-speed, fastcutting power tool with
sharp cutting blades,
special safety precautions
must be observed to
reduce the risk of
personal injury.
It is important that you
read, fully understand and
observe the following
safety precautions and
warnings. Read the
instruction manual and
the safety precautions periodically.
Careless or improper use may cause
serious or fatal injury.
Have your STIHL dealer show you how
to operate your power tool. Observe all
applicable local safety regulations,
standards and ordinances.
!Warning!
Do not lend or rent your power tool
without the instruction manual. Be sure
that anyone using it understands the
information contained in this manual.
!Warning!
The use of this machine may be
hazardous. If the cutting tool comes in
contact with your body, it will cut you.
Use your hedge trimmer only for cutting
hedges, shrubs, scrub, bushes and
similar material. It must not be used for
any other purposes, since such misuse
may result in an accident or damage to
the machine.
!Warning!
Minors should never be allowed to use
this power tool. Bystanders, especially
children, and animals should not be
allowed in the area where it is in use.
!Warning!
To reduce the risk of injury to bystanders
and damage to property, never let your
power tool run unattended. When it is
not in use (e.g. during a work break),
shut it off and make sure that
unauthorized persons do not use it.
Most of these safety precautions and
warnings apply to the use of all STIHL
hedge trimmers. Different models may
have different parts and controls. See
the appropriate section of your
instruction manual for a description of
the controls and the function of the parts
of your model.
Safe use of a hedge trimmer involves
1. the operator
2. the power tool
3. the use of the power tool.
THE OPERATOR
Physical Condition
You must be in good physical condition
and mental health and not under the
influence of any substance (drugs,
alcohol, etc.) which might impair vision,
dexterity or judgment. Do not operate
this machine when you are fatigued.
!Warning!
Be alert – if you get tired, take a break.
Tiredness may result in loss of control.
Working with any power tool can be
strenuous. If you have any condition that
might be aggravated by strenuous work,
check with your doctor before operating
this machine.
3HL 90 K
English / USA
!Warning!
Prolonged use of a power tool (or other
machines) exposing the operator to
vibrations may produce whitefinger
disease (Raynaud's phenomenon) or
carpal tunnel syndrome.
These conditions reduce the hand's
ability to feel and regulate temperature,
produce numbness and burning
sensations and may cause nerve and
circulation damage and tissue necrosis.
All factors which contribute to whitefinger disease are not known, but cold
weather, smoking and diseases or
physical conditions that affect blood
vessels and blood transport, as well as
high vibration levels and long periods of
exposure to vibration are mentioned as
factors in the development of whitefinger
disease. In order to reduce the risk of
whitefinger disease and carpal tunnel
syndrome, please note the following:
Most STIHL power tools are available
with an anti-vibration (“AV”) system
designed to reduce the transmission of
vibrations created by the machine to the
operator's hands. An AV system is
recommended for those persons using
power tools on a regular or sustained
basis.
Wear gloves and keep your hands
warm.
Keep the AV system well maintained. A
power tool with loose components or
with damaged or worn AV buffers will
tend to have higher vibration levels.
Maintain a firm grip at all times, but do
not squeeze the handles with constant,
excessive pressure. Take frequent
breaks.
All the above-mentioned precautions do
not guarantee that you will not sustain
whitefinger disease or carpal tunnel
syndrome. Therefore, continual and
regular users should closely monitor the
condition of their hands and fingers. If
any of the above symptoms appear,
seek medical advice immediately.
!Warning!
The ignition system of the STIHL unit
produces an electromagnetic field of a
very low intensity. This field may
interfere with some pacemakers. To
reduce the risk of serious or fatal injury,
persons with a pacemaker should
consult their physician and the
pacemaker manufacturer before
operating this tool.
Proper Clothing
!Warning!
To reduce the risk of injury, the operator
should wear proper protective apparel.
!Warning!
To reduce the risk of injury
to your eyes never
operate your power tool
unless wearing goggles or
properly fitted protective
glasses with adequate top
and side protection complying with ANSI
Z 87.1 (or your applicable national
standard). To reduce the risk of injury to
your face STIHL recommends that you
also wear a face shield or face screen
over your goggles or protective glasses.
!Warning!
Power tool noise may
damage your hearing.
Wear sound barriers (ear
plugs or ear mufflers) to
protect your hearing.
Continual and regular
users should have their hearing checked
regularly.
Be particularly alert and cautious when
wearing hearing protection because
your ability to hear warnings (shouts,
alarms, etc.) is restricted.
4
HL 90 K
English / USA
Always wear gloves when
handling the machine and
the cutting tool. Heavyduty, nonslip gloves
improve your grip and
help to protect your
hands.
Clothing must be sturdy
and snug-fitting, but allow
complete freedom of
movement. Wear long
pants made of heavy
material to help protect
your legs. Do not wear shorts, sandals
or go barefoot.
Avoid loose- fitting jackets,
scarfs, neckties, jewelry,
flared or cuffed pants,
unconfined long hair or
anything that could
become caught on
branches, brush or the moving parts of
the unit. Secure hair so it is above
shoulder level.
Good footing is very
important. Wear sturdy
boots with nonslip soles.
Steel-toed safety boots
are recommended.
Wear an approved safety
hard hat to reduce the risk
of injury to your head
when there is a danger of
head injuries.
THE POWER TOOL
For illustrations and definitions of the
power tool parts see the chapter on
“Main Parts and Controls”.
!Warning!
Never modify this power tool in any way.
Only attachments supplied by STIHL or
expressly approved by STIHL for use
with the specific STIHL model are
authorized. Although certain
unauthorized attachments are useable
with STIHL power tools, their use may, in
fact, be extremely dangerous.
If this tool is subjected to unusually high
loads for which it was not designed (e.g.
heavy impact or a fall), always check
that it is in good condition before
continuing work. Check in particular that
the fuel system is tight (no leaks) and
that the controls and safety devices are
working properly. Do not continue
operating this machine if it is damaged.
In case of doubt, have it checked by your
STIHL servicing dealer.
THE USE OF THE POWER TOOL
Transporting the Power Tool
!Warning!
To reduce the risk of injury from blade
contact, never carry or transport your
power tool with the cutter blades
moving.
002BA247 KN
It may be carried only in a horizontal
position. Grip the shaft in a manner that
the machine is balanced horizontally.
Keep the hot muffler away from your
body and the cutting attachment behind
you.
!Warning!
Always switch off the engine and fit the
scabbard over the cutter blades before
transporting the power tool over long
distances. When transporting it in a
vehicle, properly secure it to prevent
turnover, fuel spillage and damage to the
unit.
5HL 90 K
English / USA
Fuel
Your STIHL power tool uses an oilgasoline mixture for fuel (see the chapter on “Fuel” of your instruction manual).
!Warning!
Gasoline is an extremely
flammable fuel. If spilled
and ignited by a spark or
other ignition source, it
can cause fire and serious
burn injury or property
damage. Use extreme caution when
handling gasoline or fuel mix.
Do not smoke or bring any fire or flame
near the fuel or the power tool. Note that
combustible fuel vapor may escape from
the fuel system.
Fueling Instructions
!Warning!
Fuel your power tool in well-ventilated
areas, outdoors. Always shut off the
engine and allow it to cool before
refueling. Gasoline vapor pressure may
build up inside the fuel tank depending
on the fuel used, the weather conditions
and the tank venting system.
In order to reduce the risk of burns and
other personal injury from escaping gas
vapor and fumes, remove the fuel filler
cap on your power tool carefully so as to
allow any pressure build-up in the tank
to release slowly. Never remove the fuel
filler cap while the engine is running.
Select bare ground for fueling and move
at least 10 feet (3 m) from the fueling
spot before starting the engine. Wipe off
any spilled fuel before starting your
machine.
!Warning!
Check for fuel leakage while refueling
and during operation. If fuel leakage is
found, do not start or run the engine until
the leak is fixed and any spilled fuel has
been wiped away. Take care not to get
fuel on your clothing. If this happens,
change your clothing immediately.
Different models may be equipped with
different fuel caps.
Cap with grip
!Warning!
In order to reduce the risk of fuel spillage
and fire from an improperly tightened
fuel cap, correctly position and tighten
the fuel cap in the fuel tank opening.
To do this with this STIHL
cap, raise the grip on the
top of the cap until it is
upright at a 90° angle.
Insert the cap in the fuel
tank opening with the
triangular marks on the grip of the cap
and on the fuel tank opening lining up.
Using the grip, turn the cap firmly
clockwise as far as it will go (approx. a
quarter turn).
Fold the grip flush with the
top of the cap. If the grip
does not lie completely
flush with the cap and the
detent on the grip does
not fit in the
corresponding recess in the filler neck,
the cap is not properly seated and
tightened and you must repeat the
above steps.
6
HL 90 K
English / USA
Screw cap
!Warning!
Unit vibrations can cause
an improperly tightened
fuel filler cap to loosen or
come off and spill
quantities of fuel. In order
to reduce the risk of fuel
spillage and fire, tighten the fuel filler cap
by hand as securely as possible.
Before Starting
!Warning!
Always check your power tool for proper
condition and operation before starting,
particularly the throttle trigger, throttle
trigger interlock, stop switch and cutting
tool. The throttle trigger (if applicable)
must move freely and always spring
back to the idle position. Never attempt
to modify the controls or safety devices.
!Warning!
Never use a power tool that is damaged
or not properly maintained.
!Warning!
Check that the spark plug boot is
securely mounted on the spark plug – a
loose boot may cause arcing that could
ignite combustible fumes and cause a
fire.
Keep the handles clean and dry at all
times; it is particularly important to keep
them free of moisture, pitch, oil, grease
or resin in order for you to maintain a firm
grip and properly control your power
tool.
!Warning!
The cutting tool must be properly
tightened and in safe operating
condition. Inspect for loose parts (nuts,
screws, etc.) and for cracked, bent,
warped or damaged blades. Regularly
check the condition and tightness of the
cutter blades – with the engine stopped!
Replace damaged cutter blades before
using the power tool. Always keep
blades sharp.
STIHL recommends that you always
spray the cutter blades with STIHL resin
solvent before starting work - with the
engine stopped! You can obtain this
protective spray from your dealer. Apply
generously.
Starting
Start the engine at least 10 feet
(3 meters) from the fueling spot,
outdoors only.
002BA245 KN
For specific starting instructions, see the
appropriate section of your manual.
Place the power tool on firm ground or
other solid surface in an open area.
Maintain good balance and secure
footing.
!Warning!
To reduce the risk of injury from blade
contact, be absolutely sure that the
cutting tool is clear of you and all other
obstructions and objects, including the
ground, because when the engine starts
at starting-throttle, engine speed will be
fast enough for the clutch to engage and
move the blades on the cutting tool.
7HL 90 K
English / USA
Once the engine has started,
immediately blip the throttle trigger,
which should release the starting throttle
and allow the engine to slow down to
idle.
!Warning!
Your power tool is a one-person
machine. Do not allow other persons in
the general work area, even when
starting.
!Warning!
To reduce the risk of injury from loss of
control, do not attempt to “drop start”
your power tool.
!Warning!
When you pull the starter grip, do not
wrap the starter rope around your hand.
Do not let the grip snap back, but guide
the starter rope to rewind it properly.
Failure to follow this procedure may
result in injury to your hand or fingers
and may damage the starter
mechanism.
Important Adjustments
!Warning!
To reduce the risk of personal injury from
loss of control 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. For directions on how to adjust
idle speed, see the appropriate section
of your instruction manual.
If you cannot set the correct idle speed,
have your STIHL dealer check your
power tool and make proper
adjustments and repairs.
During Operation
Holding and controlling the power
tool
Always hold the unit firmly with both
hands on the handles while you are
working. Wrap your fingers and thumbs
around the handles.
002BA246 KN
Place your left hand on hose grip of shaft
and your right hand on rear grip and
throttle trigger. This also applies to lefthanders.
!Warning!
Never attempt to operate
your power tool with one
hand. Loss of control of
the power tool resulting in
serious or fatal injury may
result. To reduce the risk
of cut injuries, keep hands and feet away
from the cutting tool. Never touch a
moving cutting tool with your hand or
any other part of your body.
8
HL 90 K
English / USA
!Warning!
Do not overreach. Keep proper footing
and balance at all times. Special care
must be taken in slippery conditions (wet
ground, snow) and in difficult, overgrown
terrain. Watch for hidden obstacles such
as tree stumps, roots and ditches to
avoid stumbling. For better footing, clear
away fallen branches, scrub and
cuttings. Be extremely cautious when
working on slopes or uneven ground.
!Warning
To reduce the risk of injury from loss of
control, never work on a ladder, in a tree
or any other insecure support. Never
hold the machine above shoulder
height.
Working conditions
Operate and start your power tool only
outdoors in a well ventilated area.
Operate it under good visibility and
daylight conditions only. Work carefully.
!Warning!
As soon as the engine is
running, this product
generates toxic exhaust
fumes containing
chemicals, such as
unburned hydrocarbons
(including benzene) and carbon
monoxide, that are known to cause
respiratory problems, cancer, birth
defects, or other reproductive harm.
Some of the gases (e.g. carbon
monoxide) may be colorless and
odorless. To reduce the risk of serious or
fatal injury/illness from inhaling toxic
fumes, never run the machine indoors or
in poorly ventilated locations.
!Warning!
If the vegetation being cut or the
surrounding ground is coated with a
chemical substance (such as an active
pesticide or herbicide), read and follow
the instructions and warnings that
accompanied the substance at issue.
!Warning!
Inhalation of certain dusts, especially
organic dusts such as mold or pollen,
can cause susceptible persons to have
an allergic or asthmatic reaction.
Substantial or repeated inhalation of
dust and other airborne contaminants, in
particular those with a smaller particle
size, may cause respiratory or other
illnesses. Control dust at the source
where possible. Use good work
practices, 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
recommendations of EPA/OSHA/
NIOSH and occupational and trade
associations with respect to dust
(“particulate matter”). When the
inhalation of dust cannot be substantially
controlled, i.e., kept at or near the
ambient (background) level, the
operator and any bystanders should
wear a respirator approved by NIOSH/
MSHA for the type of dust encountered.
9HL 90 K
English / USA
Operating instructions
!Warning!
Do not operate your power tool using the
starting throttle lock, as you do not have
control of the engine speed.
In the event of an emergency, switch off
the engine immediately – move the slide
control / stop switch to 0 or STOP.
!Warning
The cutter blades continue to move for a
short period after the throttle trigger is
released (flywheel effect).
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.
The power tool
5m (17ft)
falling objects or inadvertent contact with
the moving cutter blades of your power
tool always keep bystanders at least 17
feet (5 m) away when the power tool is
running.
Stop the engine and cutting tool
immediately if you are approached.
has a large range.
In order to reduce
the risk of personal
or even fatal injury
to bystanders from
!Warning!
Before you start work, examine the
hedge area for stones, fence wire, metal
or other solid objects which could
damage the cutter blades.
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.
!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 carrying 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.
10
HL 90 K
English / USA
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
The gearbox becomes hot during
operation. To reduce the risk of burn
injury, do not touch the gear housing
when it is hot.
!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.
Catalytic converter
!Warning!
Some STIHL power tools
are equipped with a
catalytic converter, which
is designed to reduce the
exhaust emissions of the
engine by a chemical
process in the muffler.
Due to this process, the muffler does not
cool down as rapidly as conventional
mufflers when the engine returns to idle
or is shut off. To reduce the risk of fire
and burn injuries, the following specific
safety precautions must be observed.
!Warning!
Since a muffler with a catalytic converter
cools down less rapidly than conventional mufflers, always set your power
tool down in the upright position and
never locate it where the muffler is near
dry brush, grass, wood chips or other
combustible materials while it is still hot.
!Warning!
An improperly mounted or damaged
cylinder housing or a damaged/
deformed muffler shell may interfere
with the cooling process of the catalytic
converter. To reduce the risk of fire or
burn injury, do not continue work with a
damaged or improperly mounted
cylinder housing or a damaged/
deformed muffler shell.
11HL 90 K
English / USA
Your catalytic converter is furnished with
screens designed to reduce the risk of
fire from the emission of hot particles.
Due to the heat from the catalytic
reaction, these screens will normally
stay clean and need no service or
maintenance. If you experience loss of
performance and you suspect a clogged
screen, have your muffler maintained by
a STIHL servicing dealer.
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.
!Warning!
Use only identical STIHL replacement
parts for maintenance and repair. Use of
non-STIHL parts may cause serious or
fatal injury.
Strictly follow the maintenance and
repair instructions in the appropriate
section of your instruction manual.
Please refer to the maintenance chart in
this manual.
!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.
Wear gloves when handling or
performing maintenance on blades.
!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 modified.
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.
12
HL 90 K
Using the Hedge Trimmer
English / USA
!Warning!
Never repair damaged cutting attachments by welding, straightening or
modifying the shape. This may cause
parts of the cutting tool to come off and
result in serious or fatal injuries.
Keep the cutting tool sharp. Tighten all
nuts, bolts and screws, except the
carburetor adjustment screws, after
each use.
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.
Cutting Season
Observe country-specific or municipal
rules and regulatons for cutting hedges.
Do not use your hedge trimmer during
rest periods customary in the
neigborhood.
Cutting Sequence
If a radical cut is necessary, cut a little at
a time in several stages.
Use lopping shears to cut out thick
branches first.
Cut the sides of the hedge first, then the
top.
Recommendation: Only cut hedges
that are no higher than chest level.
Disposal
Do not throw cuttings in the garbage
can – they can be composted!
445BA001 KN
Vertical Cut
Swing the cutter bar up and down in an
arc as you move along the hedge – use
both sides of the cutting blades.
Any working position above head height
is tiring. To minimize the risk of
accidents, work in such positions for
short periods only.
13HL 90 K
English / USA
Mounting the Gearbox
Horizontal Cut
Hold the cutter bar at an angle of 0° to
10° as you swing the hedge trimmer
horizontally.
Swing the cutter bar in an arc towards
the outside of the hedge so that the
cuttings are swept on to the ground.
445BA007 KN
445BA002 KN
: Pull the protective cap off the end of
the drive tube.
When you pull off the cap, the plug
may come out of the drive tube. It
must be pushed back into the drive
tube as far as stop.
413BA014 KN
002BA248 KN
14
HL 90 K
Adjusting the Throttle Cable
English / USA
1
3
2
1
: Loosen the clamp screws (1).
: Push the gearbox (2) onto the drive
tube (3) – turn the gearbox back and
forth at the same time – until the end
of the drive can no longer be seen in
the slot in the clamp (arrows).
Continue pushing the gearbox as
far as stop.
: Position the gearbox on the drive
tube so that the machine support on
the engine points down and the
blades are horizontal.
: Tighten down the clamp screws
firmly.
A properly adjusted throttle cable is
the precondition for correct
operation in the full throttle, starting
throttle and idle positions.
Adjust the throttle cable only after
the unit is fully assembled
: Use a suitable tool to push the slide
445BA003 KN
to the bottom of the slot
1
2
: Press down the trigger interlock (1)
and squeeze the throttle trigger (2)
(full throttle) – this sets the throttle
cable correctly.
002BA163 KN
002BA161 KN
15HL 90 K
English / USA
4-MIX Engine Fuel
The STIHL 4-MIX engine features gas
oil lubrication and must be run on a fuel
mixture of gasoline and engine oil.
It operates otherwise on the 4-stroke
principle.
This engine is certified to operate on
unleaded gasoline and the STIHL twostroke engine oil at a mix ratio of 50:1.
Your engine requires a mixture of highquality gasoline and quality two-stroke
air cooled engine oil.
Use mid-grade unleaded gasoline with a
minimum octane rating of 89 (R+M/2). If
the octane rating of the mid-grade
gasoline in your area is lower, use
premium unleaded fuel.
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
nationally recognized high-quality
unleaded gasoline!
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 50:1 two-stroke
engine oil since it is specially formulated
for use in STlHL engines.
Do not use BIA or TCW rated (twostroke 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,
chainsaws, 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 canister from
your vehicle and place the canister on
the ground before filling. Do not fill fuel
canisters that are sitting in or on a
vehicle.
The canister should be kept tightly
closed in order to avoid any moisture
getting into the mixture.
The machine‘s fuel tank and the canister
in which fuel mix is stored should be
cleaned as necessary.
16
HL 90 K
Fueling
English / USA
Fuel mix ages
Only mix sufficient fuel for a few days
work, not to exceed 3 months of storage.
Store in approved fuel-canisters only.
When mixing, pour oil into the canister
first, and then add gasoline. Close the
canister and shake it vigorously by hand
to ensure proper mixing of the oil with
the fuel.
Gasoline
Oil (STIHL 50:1 or
equivalent high-quality oils)
US gal. US fl.oz
12.6
2 1/2 6.4
512.8
Dispose of empty mixing-oil canisters
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 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.
Opening the cap
249BA053 KN
: Raise the grip until it is upright.
249BA052 KN
249BA054 KN
: Turn the cap counterclockwise
(approx. a quarter turn).
: Remove the filler cap.
17HL 90 K
English / USA
Starting / Stopping
the Engine
Closing the cap
: Fit the cap – grip upright –marks
must line up.
: Turn the cap clockwise as far as
stop (approx. a quarter turn).
: Fold the grip flush with the top of the
cap.
If the grip does not lie completely flush
with the cap and the detent on the grip
does not engage the recess in the filler
neck, the cap is not properly seated and
tightened and you must repeat the
above steps.
7
STOP
3
249BA055 KN
2
1
Controls
Throttle trigger interlock (1)
Throttle trigger (2)
249BA056 KN
Slide control (3)
Positions of Slide Control
STOP-O (4) – engine off – the ignition is
switched off
# – normal run position (5) – the engine
is running or can start
START (6) - the ignition is switched on,
the engine can start
4
5
6
STOP-
START
002BA181 KN
Symbol on Slide Control
h (7) – stop symbol and arrow – to stop
the engine, push the slide control in
direction of arrow on stop symbol (h ) to
STOP-O.
Starting
: Hold down the throttle trigger
interlock and squeeze the throttle
trigger.
: While holding both levers in this
position –
: Move the slide control to START
and hold it there.
: Now release the throttle trigger,
slide control and trigger interlock in
that order. This is the starting
throttle position.
18
HL 90 K
9
8
: Set the choke knob (8):
For cold start to g
even if engine has been running but
is still cold.
For warm start to e
: Press fuel pump bulb (9) at least five
times – even if the bulb is already
filled with fuel.
249BA057 KN
: Place the unit on the ground: It must
rest securely on the engine support
and the gearbox.
: Remove the blade scabbard. Check
that the cutting blades are not
touching the ground or any other
obstacles. If necessary, rest the
gearbox on a raised support (e.g. a
mound, brick or something similar).
: Make sure you have a firm footing.
English / USA
: Hold 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. This will bend the tube
and result in permanent damage to
the drive tube.
445BA004 KN
: Pull the starter grip slowly with your
right hand until you feel it engage
and then give it a brisk strong pull.
Do not pull out the starter rope to full
length – it might otherwise break.
: Do not let the starter grip snap back.
Guide it slowly back into the housing
so that the starter rope can rewind
properly.
: Crank engine until it begins to fire.
445BA005 KN
After no more than five attempts,
turn the choke knob to e
: Continue cranking.
19HL 90 K
English / USA
When the engine begins to fire:
: Blip the throttle trigger so that the
slide control moves to the normal
run position # and the engine settles
down to idle speed.
Make sure te carburetor is properly
adjusted – the cutting blades must
not move when the engine is idling.
Your machine is now ready for
operation.
Stopping the Engine
: Move the slide control in direction of
arrow (h) to STOP-O.
At very low outside temperatures
As soon as engine runs:
: Blip the throttle trigger to disengage
the starting throttle position. The
slide control moves to the normal
run position #
and the engine settles down to idle
speed.
: Open the throttle slightly.
: Warm up engine for brief period.
If the engine does not start
Choke knob
If you did not turn the choke knob to e
quickly enough after the engine began to
fire, the combustion chamber has
flooded.
: Turn choke knob to e
: Set the slide control, trigger
interlock and throttle trigger to the
starting throttle position.
: Start the engine by pulling the
starter rope firmly. 10 to 20 pulls
may be necessary.
If the engine still does not start:
10
: Move the slide control to STOP-O.
: Pull off the spark plug boot (10).
: Unscrew and dry off the spark plug.
: Open the throttle wide.
: Crank the engine several times with
the starter to clear the combustion
chamber.
: Refit the spark plug. Connect the
spark plug boot (press it down
firmly).
: Move the slide control to START.
: Set the choke knob to e –
even if engine is cold.
: Now start the engine.
Throttle cable adjustment
: Check adjustment of throttle cable –
see chapter on "Adjusting the
Throttle Cable".
Tank run until dry
: After refueling, press the fuel pump
bulb at least five times – even if bulb
is filled with fuel.
: Set choke knob according to engine
249BA058 KN
temperature.
: Now start the engine.
20
HL 90 K
English / USA
Operating Instructions Cleaning the Air Filter
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 engine to run for a while
at idle speed so that the heat in the
engine can be dissipated by flow of
cooling air. This protects enginemounted components (ignition,
carburetor) from thermal overload.
After finishing work
Wait for engine to cool down. Drain the
fuel tank. Store the machine in a dry
place. Check tightness of nuts and
screws (not adjusting screws) at regular
intervals and retighten as necessary.
Dirty air filters reduce engine power,
increase fuel consumption and make
starting more difficult.
If there is a noticeable loss of engine
power:
: Set the choke knob to g.
: Take out the screw (1) and remove
the filter cover (2).
: Clean away loose dirt from around
the filter.
: Grip the filter element (3) at the
notch (arrow) in the filter housing (4)
and take it out.
: Fit a new filter element. As a
temporary measure you can knock it
out on the palm of your hand or blow
it out. Do not wash.
: Replace any damaged parts.
: Install filter element in the filter
housing.
: Refit the filter cover.
: Insert the screw and tighten it down
firmly.
4
2
1
Motor Management
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.
273BA006 KN
21HL 90 K
English / USA
Adjusting the Carburetor
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 and low speed
screws within fine limits.
Standard Setting
: Shut off the engine.
: Inspect cutting blades and clean if
necessary (they must be clean,
move freely and not be warped).
: Check that throttle cable is properly
adjusted – readjust if necessary –
see chapter on "Adjusting the
Throttle Cable".
: Check spark arresting screen (not
fitted in all markets) and clean or
replace as necessary.
: Check the air filter and clean or
replace as necessary.
: Carefully turn both adjusting screws
249BA051 KN
counterclockwise as far as the stop:
The high speed screw (H) and low
speed screw (L) are now 3/4 turn
open.
: Start and warm up the engine.
: Adjust idle speed with the idle speed
screw (LA) so that the cutting
blades do not run.
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 turn for every
1000m (3300 ft) change in altitude.
: Carry out the standard setting
without disturbing the high speed
screw (H) .
: Warm up the engine for about 3
minutes.
: Open the throttle wide.
22
HL 90 K
English / USA
Spark Arresting Screen in
Muffler
At high altitude
: Turn the high speed screw (H)
clockwise (leaner), no further than
stop, until there is no noticeable
increase in engine speed.
At sea level
: Turn the high speed screw (H)
counterclockwise (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 for about 3
minutes.
Engine stops while idling
: Turn idle speed screw (LA) slowly
clockwise until the engine runs
smoothly – the cutting blades must
not run.
Cutting blades run when engine is
idling
: Turn idle speed screw (LA) slowly
counterclockwise until cutting
blades stop running and then turn
the screw about another 1/2 to 3/4
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, no further than
stop, until the engine runs and
accelerates smoothly.
Erratic idling behavior
Idle setting too rich:
: Turn low speed screw (L) clockwise,
no further than stop, until the engine
runs and accelerates smoothly.
The spark arresting screen is an option
that is not fitted in all machines.
: If the engine is low on power, check
the spark arresting screen in the
muffler.
: Wait for muffler to cool down.
1
: Move slide control to STOP-O.
: Remove the screw (1).
3
2
: Remove the screws (2).
: Lift away the shroud (3).
2
249BA059 KN
249BA060 KN
23HL 90 K
English / USA
: Remove the screw (4).
: Lift spark arresting screen (5) and
pull it out.
: Clean spark arresting screen if
necessary – if screen is damaged or
coked up, fit a new one.
: Refit the spark arresting screen.
: Insert screw and tighten down.
: Fit the shroud.
Checking the Spark Plug
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,
000BA002 KN
e.g. operating at part load.
Fit a new spark plug after approx.
100 operating hours
or earlier if the electrodes are badly
eroded.
24
HL 90 K
0
Lubricating the
Gearbox
English / USA
1
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.
Lubricate the blade drive gear with
STIHL gear lubricant for hedge trimmers
– see "Special Accessories".
: Check the lubricant level at regular
intervals of about every 25 hours of
operation.
: Unscrew the filler plug (1).
00BA036 TR
: Screw the tube of grease into the
filler hole.
: Sqeeze up to 5 g (1/5 oz) grease
into the gearbox.
: Refit the filler plug and tighten it
down firmly.
Lubricate the angle drive with STIHL
gear lubricant for brushcutters – see
"Special Accessories".
: Check the lubricant level at regular
intervals of about every 25 hours of
operation.
: Unscrew the filler plug (2).
: If no grease can be seen on the
inside of the filler plug, screw the
tube of grease into the filler hole.
: Squeeze up to 5 g (1/5 oz) grease
into the gearbox.
Do not not completely fill the
gearbox with grease.
: Refit the filler plug and tighten it
down firmly.
25HL 90 K
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