STIHL HT 250 Owner's Manual
STIHL HT 250
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.
{
Instruction Manual
Manual de instrucciones
Instruction Manual
1 - 44
Manual de
instrucciones
45 - 92
Contents
English
Guide to Using this Manual 2
Safety Precautions and Working
Techniques 2
Using the Unit 14
Mounting the Bar and Chain 16
Tensioning the Chain 17
Checking Chain Tension 17
Adjusting the Throttle Cable 17
Original Instruction ManualPrinted on chlorine-free paper
Fuel 18
Fueling 19
Chain Lubricant 19
Filling Chain Oil Tank 20
Checking Chain Lubrication 21
Fitting the Harness 21
Starting / Stopping the Engine 21
Operating Instructions 23
Taking Care of the Guide Bar 24
Replacing the Air Filter 25
Engine Management 25
Adjusting the Carburetor 25
Spark Plug 27
Engine Running Behavior 28
Printing inks contain vegetable oils, paper can be recycled.
Replacing the Starter Rope and
Rewind Spring 28
Storing the Machine 30
Checking and Replacing the Chain
Sprocket 30
Maintaining and Sharpening the
Saw Chain 31
Inspections and Maintenance by
Dealer 35
Maintenance and Care 36
Main Parts 38
Specifications 40
Special Accessories 41
Maintenance and Repairs 41
STIHL Incorporated Federal
Emission Control Warranty
Statement 41
Trademarks 43
Allow only persons who fully understand
this manual to operate your pole pruner.
To receive maximum performance and
satisfaction from your STIHL pole
pruner, it is important that you read,
understand and follow the safety
precautions and the operating and
maintenance instructions in chapter
"Safety Precautions and Working
Techniques" before using your pole
pruner. For further information you can
go to www.stihlusa.com.
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 pole pruner is a high-speed,
fast-cutting power tool with a very long
reach, special safety precautions must
be observed to reduce the risk of personal injury. Careless or improper use
may cause serious or even fatal injury.
{
© ANDREAS STIHL AG & Co. KG, 2011
0458-275-8621-A. M0-55.E11.PM.
0000000847_004_GB
HT 250
1
English
Guide to Using this Manual
Pictograms
All the pictograms attached to or
embossed on the machine are shown
and explained in this manual.
Symbols in Text
Many operating and safety instructions
are supported by illustrations.
The individual steps or procedures
described in the manual may be marked
in different ways:
N A bullet marks a step or procedure.
A description of a step or procedure that
refers directly to an illustration may
contain item numbers that appear in the
illustration. Example:
N Loosen the screw (1).
N 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 and signal words described
below:
Danger!
Indicates an imminent risk of severe or
fatal injury.
Warning!
Indicates a hazardous situation which, if
not avoided, could result in severe or
fatal injury.
Caution!
Indicates a risk of property damage,
including damage to the machine or its
individual components.
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. Therefore,
some changes, modifications and
improvements may not be covered in
this manual. If the operating
characteristics or the appearance of
your machine differ from those
described in this manual, please contact
your STIHL dealer for assistance.
Safety Precautions and
Working Techniques
Because a pole pruner is
a high-speed, fast-cutting power tool with a
very long reach, 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. The pole pruner chain has many
sharp cutters. If the cutters contact your
flesh, they will cut you, even if the chain
is not moving.
Do not cut any material other than wood
or wooden objects. Use your pole pruner
for limbing only.
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Warning!
Do not use it for other purposes, since
misuse may result in personal injury or
property damage, including 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
pole pruners. 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 pole pruner 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.
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 elements 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.
HT 250
3
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390BA000 KN
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 protec-
tive 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.
Wear an approved safety hard hat to
reduce the risk of injury to your head.
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.
Always wear gloves
when handling the
machine and the cutting
tool. Heavy-duty, 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
with cut retardant inserts
are recommended.
THE POWER TOOL
For illustrations and definitions of the
power tool parts see the chapter on
"Main Parts".
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
This power tool should 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. Accidental
4
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001BA220 KN
acceleration of the engine can cause the
chain to rotate and cause serious
injuries.
Warning!
Always switch off the engine and fit the
scabbard over the cutting attachment
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.
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 seri-
ous 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!
To reduce the risk of serious injury from
burns, never attempt to refuel the unit
until it has been completely removed
from the operator.
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.
Toolless 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 raised positioning
marks on the grip of the cap and on the
fuel tank opening lining up. Using the
grip, press the cap down firmly while
turning it clockwise as far as it will go
(approx. 1/4 turn).
Fold the grip flush with
the top of the cap. Grip
the cap and check for
tightness. 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
opening, or if the cap is
loose in the filler opening,
the cap is not properly
seated and tightened and
you must repeat the
above steps.
HT 250
5
English
001BA227 KN
001BA226 KN
Misaligned, damaged or broken cap
N If the cap does not drop fully into the
opening when the positioning marks
line up and/or if the cap does not
tighten properly when twisted, the
base of the cap may be prematurely
rotated (in relation to the top) to the
closed position. Such misalignment
can result from handling, cleaning
or an improper attempt at
tightening.
Left: Base of cap in closed posi-
tion (with open space)
Right: Base of cap correctly posi-
tioned for installation
N To return the cap to the open
position for installation, turn the cap
(with the grip up) until it drops fully
into the tank opening. Next, twist 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. Then, twist the cap
clockwise, closing it normally.
N If your cap still does not tighten
properly, it may be damaged or
broken; immediately stop use of the
unit and take it to your authorized
STIHL dealer for repair.
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.
See also the "Fueling" chapter in your
Instruction Manual for additional
information.
Before Starting
Take off the chain guard (scabbard) and
inspect the pole pruner for proper
condition and operation. (See the
maintenance chart near the end of the
instruction manual.)
Warning!
Always check your power tool for proper
condition and operation before starting,
particularly the throttle trigger, throttle
trigger lockout, stop switch and cutting
attachment. The throttle trigger must
move freely and always spring back to
the idle position. Never attempt to modify the controls or safety devices.
Warning!
Never operate your power tool if it is
damaged, improperly adjusted or maintained, or not completely or securely
assembled.
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, fuel mix,
grease or resin in order for you to
maintain a firm grip and properly control
your power tool.
For proper assembly of the bar and
chain follow the procedure described in
the chapter "Mounting the Bar and
Chain" of your instruction manual.
STIHL Oilomatic chain, guide bar and
sprocket must match each other in
gauge and pitch.
Warning!
Proper chain tension is extremely
important. In order to avoid improper
setting, the tensioning procedure must
be followed as described in your manual. Always make sure the hex nut(s) for
the sprocket cover is (are) tightened
securely after tensioning the chain.
Check chain tension once more after
having tightened the nut(s). Never start
the pole pruner with the sprocket cover
loose.
6
HT 250
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275BA006 KN
Adjust carrying harness and hand grip to
suit your size before starting work.
Starting
To reduce the risk of fire and burn
injuries, start the engine at least 10 feet
(3 m) from the fueling spot, outdoors
only.
Start and operate your pole pruner
without assistance.
For specific starting instructions, see the
appropriate section of your manual.
Proper starting methods reduce the risk
of injury.
Place the pole pruner on firm ground or
other solid surface in an open area or, in
the alternative, as shown in the above
picture. Maintain good balance and
secure footing.
Warning!
To reduce the risk of injury from loss of
control, do not attempt to "drop start"
your power tool.
Warning!
To reduce the risk of injury from loss of
control be absolutely sure that the guide
bar and chain are 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 the sprocket and turn the
chain.
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.
With the engine running only at idle,
attach the power tool to the spring hook
of your harness (see appropriate
chapter of this manual).
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 saw chain 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.
Proper chain tension is very important at
all times. Check it at regular intervals
(whenever the pole pruner is shut off). If
the chain becomes loose while cutting,
switch off the engine and then tighten.
Never try to tighten the chain while the
engine is running.
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.
HT 250
7
English
390BA026 KN
Place your left hand on the shaft and
your right hand on rear grip and throttle
trigger. Left-handers should follow these
instructions, too. Keep your hands in this
position to have your pole pruner under
control at all times.
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.
Warning!
In order to properly control your pole
pruner, always maintain good balance
and a firm foothold. Never work on a
ladder, in a tree or on any other insecure
support. Never hold the machine above
shoulder height. Do not overreach.
When working at a height above 15 feet
(4.5 m) use a lift bucket. For pole pruner
with adjustable shaft, expand the shaft
only as far as necessary for the
intended application.
Warning!
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, rocks, holes 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!
Take extreme care in wet and freezing
weather (rain, snow, ice). Put off the
work when the weather is windy, stormy
or rainfall is heavy.
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.
If exhaust fumes become concentrated
due to insufficient ventilation, clear
obstructions from work area to permit
proper ventilation before proceeding
and / or take frequent breaks to allow
fumes to dissipate before they become
concentrated.
8
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15m (50ft)
15m (50ft)
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. This includes wood dust,
especially from hardwoods, but also
from some softwoods such as Western
Red Cedar. Control dust at the source
where possible. Use good work practices, such as such as always cutting
with a properly sharpened chain (which
produces wood chips rather than fine
dust) and 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.
Warning!
Breathing asbestos dust is dangerous
and can cause severe or fatal injury,
respiratory illness or cancer. The use
and disposal of asbestos-containing
products have been strictly regulated by
OSHA and the Environmental Protection Agency. If you have any reason to
believe that you might be cutting asbestos, immediately contact your employer
or a local OSHA representative.
Warning!
This power tool has a large range. In
order to reduce the risk of personal or
even fatal injury to bystanders from falling objects or inadvertent contact with
the moving chain of your power tool
always keep bystanders at least 50 feet
(15 m) away when the power tool is
running.
Warning!
Even though bystanders should be kept
away from the running saw, never work
alone. Keep within calling distance of
others in case help is needed.
Stop the engine immediately if you are
approached.
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.
Electricity can jump from one point to
another by means of arcing. Higher
voltage increases the distance electricity
can arc. Electricity can also move
through branches, especially if they are
wet. Maintain a clearance of at least
50 feet (15 m) between the pole pruner
(including any branches it is contacting)
and any electrical line carrying live
current. Before working with less
clearance, contact your electric utility
and make sure the current is turned off.
HT 250
9
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275BA005 KN
Operating Instructions
Warning!
Do not operate your power tool using
the starting throttle position, 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!
To reduce the risk of cut injuries, keep
hands and feet away from the saw
chain. Never touch a moving chain with
your hand or any other part of your
body. The saw chain continues to move
for a short period after the throttle trigger
is released (inertia effect).
Accelerating the engine while the chain
is 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 chain moving while the engine
is idling.
Warning!
If the chain becomes clogged, always
turn off the engine and make sure the
chain has stopped before cleaning.
Make sure that the saw chain does not
touch any foreign materials such as
rocks, fences, nails and the like. Such
objects may be flung off and injure the
operator or bystanders, or damage the
saw chain.
Warning!
Prior to limbing, clear the working area
from interfering limbs and brush. Then,
establish an escape area away from
where the cut limbs can fall, and remove
all obstacles.
Keep work area clear – move away
fallen limbs. Place all tools and
equipment at a safe distance from the
branches being limbed, but not in the
escape area.
Warning!
Always observe the general condition of
the tree. Look for decay and rot in the
trunk and branches. If it is rotted inside,
it could snap and fall toward the operator while being cut. Also look for broken
or dead branches which could vibrate
loose and fall on the operator. If branch
is thick or heavy, make a shallow relief
cut on the bottom of the branch before
cutting down from the top to help prevent splitting of the branch.
Warning!
To reduce the risk of severe or even
fatal injury from falling objects do not cut
vertically above your body. Hold the
pole pruner at an angle of not more than
60° from the horizontal level (see picture). Objects may fall in unexpected
directions. Do not stand directly underneath the limb being cut!
Watch for falling wood! As soon as the
limbed branch starts to fall, step aside
and keep a sufficient distance away from
the falling wood.
10
HT 250
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Warning!
Always pull the unit out of the cut with
the chain running to reduce the possibility of pinching the cutting attachment.
Don't put pressure on the pole pruner
when reaching the end of a cut. The
pressure may cause the bar and rotating chain to pop out of the cut or kerf, go
out of control and strike some other
object.
If the bar becomes pinched and caught
in the branch so that the chain can no
longer move, shut off the pole pruner
and carefully move the branch to open
the pinch and release the bar.
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!
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.
Catalytic Converter Your catalytic converter is furnished with
screens designed to reduce the risk of
fire from the emission of hot particles.
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
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.
Reactive Forces
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!
Reactive forces may occur any time the
chain is rotating.The force used to cut
wood can be reversed and work against
the operator. If the rotating chain is sud-
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.
denly stopped by contact with any solid
object such as a branch or is pinched,
the reactive forces may occur instantly.
These reactive forces may result in loss
of control, which, in turn, may cause
personal injury. An understanding of the
causes of these reactive forces may
help you avoid the element of surprise
and loss of control.
Because of the design of the pole
pruner, the reactive forces experienced
when working with it are generally not as
severe as those encountered with a
chainsaw. Nevertheless, you should
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11
English
002BA230 KN
001BA037 KN
A
001BA038 KN
B
always maintain a proper grip and good
footing to control the power tool when
you experience such forces.
The most common reactive forces are:
– kickback,
– pushback,
– pull-in.
Kickback
Kickback may occur when the moving
saw chain near the upper quadrant of
the bar nose contacts a solid object or is
pinched.
The reaction of the cutting force of the
chain causes a rotational force on the
chainsaw in the direction opposite to the
chain movement. This may cause the
bar to move upward.
To Avoid Kickback
The best protection from kickback is to
avoid kickback situations:
1. Be aware of the location of the guide
bar nose at all times.
2. Never let the nose of the guide bar
contact any object. Do not cut limbs
with the nose of the guide bar. Be
especially careful near wire fences
and when cutting small, tough
limbs, which may easily catch the
chain.
3. Cut only one limb at a time.
A = Pull-in
Pull-in occurs when the chain on the
bottom of the bar is suddenly stopped
when it is pinched, caught or encounters
a foreign object in the wood. The
reaction of the chain pulls the saw
forward.
Pull-in frequently occurs when the chain
is not rotating at full speed before it
contacts the wood.
To Avoid Pull-in
1. Be alert to forces or situations that
may cause material to pinch the
chain at the bottom of the bar.
2. Always start a cut with the chain
rotating at full speed.
B = Pushback
Pushback occurs when the chain on the
top of the bar is suddenly stopped when
it is pinched, caught or encounters a
foreign object in the wood. The reaction
of the chain may drive the saw rapidly
straight back toward the operator.
Pushback frequently occurs when the
top of the bar is used for cutting.
To Avoid Pushback
1. Be alert to forces or situations that
may cause material to pinch the
chain at the top of the bar.
2. Do not cut more than one limb at a
time.
3. Do not twist the bar when
withdrawing it from an underbuck
cut because the chain can pinch.
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
12
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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
sections of your instruction manual.
Please refer to the maintenance chart in
this manual.
Warning!
Always stop the engine and make sure
that the chain 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 the cutting
attachment.
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.
English
Warning!
Keep the chain, bar and sprocket clean;
replace worn sprockets or chains. Keep
the chain sharp. You can spot a dull
chain when easy-to-cut wood becomes
hard to cut or burn marks appear on the
wood. Keep chain at proper tension.
Tighten all nuts, bolts and screws except
the carburetor adjustment screws after
each use.
For maintenance items please also refer
to the maintenance chart in this manual.
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.
Store fuel and chain oil in approved and
properly labeled safety-type canisters
only. Take care when handling gasoline!
Avoid direct contact with the skin and
avoid inhaling fuel vapor!
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275BA002 KN
390BA052 KN
2
1
390BA041 KN
Using the Unit
Preparations
N Wear suitable protective clothing,
observe safety precautions.
N Starting the engine
N Put on the shoulder strap.
Cutting Sequence
To allow branches a free fall, always cut
the lower branches first. Prune heavy
branches (large diameter) in several
controllable pieces.
Never stand directly underneath
the branch you are cutting – be
wary of falling branches. Note that
a branch may spring back at you
after it hits the ground – risk of
injury.
Disposal
Do not throw cuttings into the garbage
can – they can be composted.
Working Techniques
The shaft should always be held at an
angle of 60° or less.
The least tiring working position is a tool
angle of 60°.
Any lesser angle may be used to suit the
situation concerned.
Cross-cut
Relieving cut
To avoid tearing the bark on thick
branches, always start by performing a
relieving cut (1) on the underside of the
branch.
N To do this, apply the cutting
attachment and pull it across the
bottom of the branch in an arc as far
as the bar nose.
N Then position the bar with the hook
against the branch and perform the
cross-cut (2).
Hold the control handle with your right
hand, and the shaft with your left hand.
Your left arm should be extended to the
most comfortable position.
Always hold the shaft with your left hand
in the area of the handle hose.
14
To avoid pinching the bar in the cut,
position the cutting attachment with the
hook against the branch and then
perform the cross-cut from the top
downwards.
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3
4
A
390BA024 KN
275BA003 KN
275BA008 KN
1
2
390BA053 KN
Flush-cutting thick branches
If branch diameter is more than
4in(10cm), first
N perform an initial cut (3), with
relieving cut and cross-cut at
distance (A) of about 8 in (20 cm)
from the final cut, then carry out the
flush-cut (4), starting with a relieving
cut and finishing with a cross-cut.
Cutting above obstacles
The unit's long reach makes it possible
to prune branches that are overhanging
obstacles, such as rivers or lakes. The
tool angle in this case depends on the
position of the branch.
Cutting from a lift bucket
30° angle drive (special accessory)
The angle drive keeps the cutting
attachment at an angle of 30° to the
drive tube.
The angle drive may be adjusted on the
drive tube to the following positions only:
1 For cross-cutting vertical branches
and bushes.
2 For a better view of the cutting
attachment.
HT 250
The unit's long reach enables cutting to
be performed next to the trunk without
the risk of the lift bucket damaging other
branches. The tool angle in this case
depends on the position of the branch.
15
English
390BA042 KN
1
2
390BA043 KN
390BA003 KN
1
5
390BA044 KN
4
3
Mounting the Bar and
Chain
Removing the chain sprocket cover
N Unscrew the nut and remove the
cover.
Fitting the chain
Wear work gloves to protect your
hands from the sharp cutters.
N Fit the chain – start at the bar nose.
N Fit the guide bar over the screw (3)
and engage peg of tensioner slide in
the hole (4) – place the chain over
the sprocket (5) at the same time.
N Turn the tensioning screw (1)
clockwise until there is very little
chain sag on the underside of the
bar – and the drive link tangs are
engaged in the bar groove.
N Refit the cover and screw on the nut
fingertight.
N Go to chapter on "Tensioning the
Saw Chain"
N Turn the screw (1)
counterclockwise until the tensioner
slide (2) butts against the left end of
the housing slot, then back it off 5
full turns.
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1
390BA045 KN
390BA046 KN
002BA163 KN
2
1
002BA161 KN
Tensioning the Chain
Retensioning during cutting work:
N Stopping the engine
N Loosen the nut.
N Hold the bar nose up.
N Use a screwdriver to turn the
tensioning screw (1) clockwise until
the chain fits snugly against the
underside of the bar.
N While still holding the bar nose up,
tighten down the nut firmly.
N Go to "Checking Chain Tension".
A new chain has to be retensioned more
often than one that has been in use for
some time.
N Check chain tension frequently –
see chapter on "Operating
Instructions".
Checking Chain Tension
N Shut off the engine
N Wear work gloves to protect your
hands.
N The chain must fit snugly against
the underside of the bar and it must
still be possible to pull the chain
along the bar by hand.
N If necessary, retension the chain.
A new chain has to be retensioned more
often than one that has been in use for
some time.
N Check chain tension frequently –
see chapter on "Operating
Instructions".
Adjusting the Throttle
Cable
A properly adjusted throttle cable is the
precondition for correct operation in the
full throttle, starting throttle and idle
positions.
N Adjust the throttle cable only when
the unit is completely and properly
assembled.
N Use a suitable tool to push the slide
to the end of the slot (see
illustration).
N Press down the throttle trigger
lockout (1) and squeeze the throttle
trigger (2) (full throttle) – this sets
the throttle cable correctly.
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Fuel
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 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.
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.
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 (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,
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.
Gasoline
US gal. US fl.oz.
12.6
2 1/2 6.4
5 12.8
Dispose of empty mixing-oil containers
only at authorized disposal locations.
Oil (STIHL 50:1 or equivalent high-quality oils)
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256BA060 KN
250BA051 KN
Fueling
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 can 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 buildup in the tank to release slowly.
After fueling, tighten down the
filler cap by hand as securely as
possible.
Change the fuel pickup body every
year.
Before storing your machine for a long
period, drain and clean the fuel tank.
Run the engine until the carburetor is
dry.
Chain Lubricant
For automatic and reliable lubrication of
the chain and guide bar – use only an
environmentally compatible quality
chain and bar lubricant. Rapidly
biodegradable STIHL Bioplus is
recommended.
Biological chain oil must be
resistant to aging (e.g. STIHL
Bioplus) since it will otherwise
quickly turn to resin. This results
in hard deposits that are difficult to
remove, especially in the area of
the chain drive and chain. It may
even cause the oil pump to seize.
The service life of the chain and guide
bar depends on the quality of the
lubricant. It is therefore essential to use
only a specially formulated chain
lubricant.
Do not use waste oil. Renewed
contact with waste oil can cause
skin cancer. Moreover, waste oil is
environmentally harmful.
Waste oil does not have the
necessary lubricating properties
and is unsuitable for chain
lubrication.
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390BA047 KN
402BA036 KN
402BA037 KN
Filling Chain Oil Tank
A full chain oil tank is sufficient for
only half a tankful of fuel. Check
the oil level regularly during
cutting work. Never allow the oil
tank to run dry.
Preparations
N Thoroughly clean the oil filler cap
and the area around it to ensure that
no dirt falls into the tank.
N Position the machine so that the
filler cap is facing up.
Opening the filler cap
The bayonet-type oil tank filler cap with
hinged grip can be opened and closed
without tools.
N To open the tank, swing the grip to
the vertical position.
N Turn the filler cap counterclockwise
as far as stop and remove.
Filling up with chain oil
N Filling up with chain oil
Take care not to spill chain oil while
refilling and do not overfill the tank.
Closing the filler cap
N To close the oil tank, place the filler
cap in position with the grip upright,
making sure the recesses are in
alignment.
N Turn the filler cap clockwise as far
as stop.
N Fold the grip down so that it is flush
with the top of the cap.
If the oil level in the tank does not go
down, the reason may be a fault in the oil
supply system: Check chain lubrication,
clean the oilways, contact your dealer
for assistance if necessary STIHL
recommends that you have servicing
and repair work carried out exclusively
by an authorized STIHL servicing
dealer.
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English
390BA048 KN
2
1
390BA040 KN
3
STOP
2
5
6
4
7
002BA181 KN
START
STOP-
1
Checking Chain
Lubrication
The saw chain must always throw off a
small amount of oil.
Never operate your saw without
chain lubrication. If the chain runs
dry, the whole cutting attachment
will be irretrievably damaged
within a very short time. Always
check chain lubrication and the oil
level in the tank before starting
work.
Every new chain has to be broken in for
about 2 to 3 minutes.
After breaking in the chain, check chain
tension and adjust if necessary – see
"Checking Chain Tension".
Fitting the Harness
The type and style of the harness
depend on the market.
Shoulder strap
N Put on the shoulder strap (1).
N Adjust the length of the strap.
N With the power tool attached, the
carabiner (2) must be at about the
same height as your right hip.
Starting / Stopping the
Engine
Controls
1 Throttle trigger lockout
2 Throttle lever
3 Slide control
Positions of slide control
4STOP-0 – engine off – the ignition is
switched off
5 F – normal run position – the engine
is running or can start
6 START – the ignition is switched on
– the engine can start
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21
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250BA018 KN
9
8
275BA007 KN
Symbol on slide control
7 h – stop symbol and arrow. To stop
the engine, push the slide control in
the direction of the arrow on the stop
symbol (h) to STOP-0.
Starting
N Press down the throttle trigger
lockout lever and squeeze the
throttle trigger.
N and hold them in that position.
N Move the slide control to START
and hold it there.
N Now release the throttle trigger,
slide control and throttle trigger
lockout in that order. This is the
starting throttle position.
N Set the choke knob (8):
g If the engine is cold
e for warm start – also use this posi-
tion if the engine has been running
but is still cold.
N Press the fuel pump bulb (9) at least
five times – even if the bulb is
already filled with fuel.
Starting
N Remove the chain guard.
22
N Place the unit on the ground: It must
rest securely on the engine support
and the hook. If necessary, rest the
hook on a raised support (e.g. a
branch, mound or something
similar). Check that the chain is not
touching any object or the ground.
Check that nobody is standing
within the working range of the
pruner.
N Make sure you have a safe and
secure footing.
N Hold the unit with your left hand on
the fan housing and press it down
firmly – your thumb should be
under the fan housing.
Do not stand or kneel on the drive
tube.
Alternative method:
N Remove the chain guard. Position
the shaft on a branch so that it is
held by the hook – check that the
chain is not touching any object or
the ground.
N Hold the unit firmly with your left
hand on the fan housing – your
thumb should be under the fan
housing.
N Hold the starter grip with your right
hand.
N Pull the starter grip slowly until you
feel it engage and then give it a brisk
strong pull.
Do not pull out the starter rope all
the way – it might otherwise
break.
N Do not let the starter grip snap back.
Guide it slowly back into the housing
so that the starter rope can rewind
properly.
N Crank the engine until it begins to
fire. After no more than five
attempts, turn the choke knob to e.
When the engine begins to fire:
N Continue cranking.
HT 250
English
As soon as the engine runs
N Blip the throttle trigger. The slide
control moves to the normal run
position F – and the engine settles
down to idle speed.
Make sure the carburetor is
correctly adjusted. The saw chain
must not rotate when the engine is
idling.
Your machine is now ready for
operation.
Stopping the engine
N Push the slide control in the
direction of the arrow on the stop
symbol (h) to STOP-0.
At very low outside temperatures:
As soon as the engine runs:
N Blip the throttle trigger to disengage
the starting throttle position. The
slide control moves to the normal
run position F – and the engine
settles down to idle speed.
N Open the throttle slightly.
N Warm up the engine for a short
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 is flooded.
N Turn the choke knob to e
N Set the slide control, throttle trigge
lockout lever and throttle trigger to
the starting throttle position.
N Start the engine by pulling the
starter rope briskly – 10 to 20 pulls
may be necessary.
If the engine still does not start
N Move the slide control to STOP-0.
N Remove the spark plug – see
"Spark Plug".
N Dry the spark plug.
N Open the throttle wide.
N Crank the engine several times with
the starter to clear the combustion
chamber.
N Refit the spark plug – see "Spark
Plug".
N Move the slide control to START.
N Set the choke knob to e – even if
the engine is cold.
N Now start the engine.
Throttle cable adjustment
N Check adjustment of throttle cable –
see chapter on "Adjusting the
Throttle Cable".
Fuel tank run until completely dry
N After refueling, press the fuel pump
bulb at least five times – even if the
bulb is filled with fuel.
N Set the choke knob according to
engine temperature.
N Start the engine.
Operating Instructions
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
Do not make the mixture leaner to
achieve an apparent increase in
power – this could damage the
engine – see "Adjusting the
Carburetor".
Check chain tension frequently
A new chain has to be retensioned more
often than one that has been in use for
some time.
Chain cold
Tension is correct when the chain fits
snugly against the underside of the bar
and can still be pulled along the bar by
hand. Retension if necessary – see
"Tensioning the Saw Chain".
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23
English
3
2
1
390BA050 KN
Chain at operating temperature
The chain stretches and begins to sag.
The drive links must not come out of the
bar groove – the chain may otherwise
jump off the bar. Retension the chain –
see "Tensioning the Saw Chain".
The chain contracts as it cools
down. If it is not slackened off, it
can damage the gear shaft and
bearings.
After long period of full-throttle
operation
Allow engine to run for a short while at
idle speed so that engine heat can be
dissipated by the flow of cooling air. This
protects engine-mounted components
(ignition, carburetor) from thermal
overload.
After Finishing Work
N Slacken off the chain if you have
retensioned it at operating
temperature during cutting work.
Always slacken off the chain after
finishing work. The chain
contracts as it cools down. If it is
not slackened off, it can damage
the gear shaft and bearings.
Storing your saw for a short period
Wait for the engine to cool down. Drain
the fuel tank. Store the machine in a dry
location. Check the tightness of all
accessible screws and nuts (not
adjusting screws) at regular intervals
and retighten if necessary.
Storing for a long period
See chapter on "Storing the Machine"
Taking Care of the Guide
Bar
N Turn the bar over – every time you
sharpen the chain and every time
you replace the chain – this helps
avoid one-sided wear, especially at
the nose and underside of the bar.
N Regularly clean the oil inlet hole (1),
the oilway (2) and the bar
groove (3).
N Measure the groove depth – with
the scale on the filing gauge (special
accessory) – in the area used most
for cutting.
Chain type Chain pitch Minimum
groove
depth
Picco 3/8" P 0.20"
(5.0 mm)
Rapid 1/4" 0.16"
(4.0 mm)
If groove depth is less than specified:
N Replace the guide bar.
The drive link tangs will otherwise
scrape along the bottom of the groove –
the cutters and tie straps will not ride on
the bar rails.
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English
1
2
3
250BA022 KN
Replacing the Air Filter
If there is a noticeable loss of engine
power
N Turn the choke knob to g
N Press in the tab (1) and remove the
filter cover (2).
N Clean away loose dirt from around
the air filter (3) and inside the filter
cover.
N Remove the filter element and
check it – replace if dirty or
damaged.
N Install the filter element in the filter
housing.
N Fit the filter cover.
Engine Management Adjusting the Carburetor
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.
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
N Stopping the engine
N Check chain tension
N Check the air filter and replace it if
necessary.
N Check that the throttle cable is
properly adjusted – readjust if
necessary – see chapter on
"Adjusting the Throttle Cable".
N Have the spark arresting screen
(not fitted in all markets) checked,
and cleaned or replaced if
necessary – see “Inspection and
Maintenance by Dealer"
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25
English
LA
H
L
1
250BA039 KN
N Turn high speed screw (H)
counterclockwise as far as stop (no
more than 3/4 turn).
N Turn the low speed screw (L)
carefully clockwise as far as stop,
then turn it back 1 turn.
N Start and warm up the engine.
N Adjust idle speed with the idle speed
screw (LA) so that the saw chain
does not rotate.
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 eighth of a turn for every 3300 ft
(1000 m) change in altitude.
Conditions for adjustment
N Carry out the standard setting.
N Warm up the engine.
N Open the throttle wide.
At high altitude
N Turn the high speed screw (H)
clockwise (leaner), no further than
stop, until there is no further
noticeable increase in engine
speed.
At sea level
N 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.
Readjust idle
It is usually necessary to change the
setting of the idle speed screw (LA) after
every correction to the low speed
screw (L).
N Warm up the engine.
Engine stops while idling
N Turn the idle speed screw (LA)
slowly clockwise until the engine
runs smoothly – the saw chain must
not rotate.
Chain runs when engine is idling
N Turn the idle speed screw (LA)
counterclockwise until the saw
chain stops moving and then rotate
the screw another 1/2 to 1 turn in
the same direction.
If the chain continues moving
when the engine is idling, have
your power tool checked and
repaired by your servicing dealer.
Erratic idling behavior, engine stops
even though setting of LA-screw has
been corrected, poor acceleration
Idle setting is too lean:
N Idle setting is too lean: Rotate the
low speed screw (L) about 1/4 turn
counterclockwise until the engine
runs and accelerates smoothly.
Erratic idling behavior
Idle setting is too rich
N Rotate the low speed screw (L)
about 1/4 turn clockwise until the
engine runs and accelerates
smoothly.
26
HT 250
English
1
249BA063 KN
000BA039 KN
A
2
1
002BA363 KN
Spark Plug
If engine is down on power, difficult to
start or runs poorly at idling speed, first
check the spark plug.
Fit a new spark plug after approx. 100
operating hours or earlier if the
electrodes are badly eroded.
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.
Removing the spark plug
N Move the slide control to STOP-0.
N Pull off the spark plug boot (1).
N Unscrew the spark plug.
Checking the Spark Plug
N Clean dirty spark plug.
N Check electrode gap (A) and
readjust if necessary – see
"Specifications".
N 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.
Warning!
To reduce the risk of fire and burn injury,
use only spark plugs authorized by
STIHL. Always press spark plug boot (1)
snugly onto spark plug terminal (2) 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.
HT 250
27
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