STIHL SR 420, SR 340 Owner's Manual
STIHL SR 340, 420
STIH)
Instruction Manual
Manual de instrucciones
Warning!
For safe operation follow all safety
precautions in Instruction Manual - improper
use can cause serious injury.
Advertencia!
Para su seguridad durante el manejo de este
producto, siga siempre las precauciones de
seguridad dadas en el manual de
instrucciones - el uso indebido puede causar
lesiones graves.
Contents
English / USA
Guide to Using this Manual .............. 2
Safety Precautions and
Working Techniques ......................... 3
Assembling the Machine ................ 14
Harness .......................................... 16
Fuel ................................................ 17
Fueling ............................................ 18
BA_SE_004_007_01_05.fmPrinted on chlorine-free paper.
Information Before You Start .......... 18
Starting / Stopping the Engine ........ 19
Calculating Required Quantity
of Solution ...................................... 22
Metering Unit .................................. 23
Filling the Container ........................ 25
Mistblowing ..................................... 25
Cleaning the Air Filter ..................... 26
Motor Management ........................ 27
Adjusting the Carburetor ................ 27
Spark Arresting Screen
in Muffler ......................................... 29
Checking the Spark Plug ................ 29
Replacing Starter Rope and
Rewind Spring ................................ 30
Storing the Machine ........................ 33
Maintenance Chart ......................... 34
Parts and Controls .......................... 35
Specifications ................................. 37
Printing inks contain vegetable oils; paper can be recycled.
Special Accessories ....................... 38
Maintenance and Repairs ............... 38
STIHL Incorporated
Federal Emission Control
Warranty Statement ........................ 39
Trademarks .................................... 41
Allow only persons who understand this
Manual to operate your mistblower.
To receive maximum performance and
satisfaction from your STIHL mistblower,
it is important that you read and
understand the maintenance and safety
precautions, starting on page 3, before
using your mistblower.
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 mistblower is a tool for
spraying chemicals, some special safety
precautions must be observed as with
any other power tool 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 mistblower differs
from those described in this Manual,
please contact your STIHL dealer for
information and assistance.
STIHl
© ANDREAS STIHL AG & Co. KG, 2006
0458 37 2 8621 A. M 0,8. J6. PM . Prin ted in USA
1SR 340, SR 420
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
SR 340, SR 420
Safety Precautions and
Working Techniques
English / USA
Because the mistblower is
a tool for spraying
chemicals, 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
general safety
precautions and
warnings. Read the
instruction manual and the safety
precautions periodically. In addition,
read and follow the chemical
manufacturer’s instructions for the
chemical products being applied. Since
such products may vary greatly in
handling/application requirements and
risks, the product label is normally your
best guide for safe and effective use.
!Warning!
Read the label each time before mixing
or using the chemical and before storing
or disposing of it. Do not trust your
memory. 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.
All operating and servicing personnel
should be trained and familiarized with
the proper handling procedures for the
chemical products being used, as well
as with first aid/emergency care, and
liquid chemical disposal regulations.
!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 chemicals sprayed with your power
tool may contain toxic and/or caustic
substances. Such chemicals can be
dangerous and cause serious or fatal
injury to persons and animals and/or
severe damage to plants and the
environment.
Avoid direct contact with chemicals.
Follow the chemical manufacturer’s
instructions with respect to any contact
with its product.
Use your power tool for spraying
chemicals and other liquids to control
pests and weeds in fruit, flower and
vegetable gardens, on trees and bushes
and on other plants, such as coffee,
tobacco and cotton. It is also useful in
the maintenance of young trees,
controlling the bark beetle and other
plant diseases.
!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
mistblowers. 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 mistblower involves
1. the operator
2. the power tool
3. the use of the power tool
4. the handling of the chemicals to be
sprayed.
3SR 340, SR 420
English / USA
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 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 when working
with chemical agents, the operator
should wear proper protective apparel
when filling, using and cleaning the
power tool. Always follow all of the
chemical manufacturer’s instructions
with respect to proper eye, skin, nose
and mouth protection. They may differ
from and exceed the following
precautions.
4
SR 340, SR 420
English / USA
!Warning!
To reduce the risk of injury
to your eyes you may
need to wear protective
goggles when operating
your power tool. Check
the product label for the
chemical you are spraying.
Always wear rubber/
chemical-resistent gloves
when handling the power
tool.
For some chemicals it is
advisable to wear
impermeable coveralls or
an impermeable work
apron. Check the product
label. If you are spraying
overhead or if the spray may reach head
height, wear a wide brim hat or other
suitable head covering. Do not wear
shorts, sandals or go barefoot.
Wear rubber/chemical-
resistent boots.
!Warning!
When working with toxic chemicals, the
operator and any bystanders may need
to wear a properly fitted respirator
approved by NIOSH/MSHA for the
chemical being used. Consult the
product label. Breathing toxic chemicals
can cause serious or fatal injury.
!Warning!
Power tool noise may
damage your hearing.
Wear sound barriers (ear
plugs or ear mufflers) to
help 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.
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.
!Warning!
Mistblowers may usually also be used in
greenhouses that are well ventilated if
the operator can protect himself or
herself from any harmful effects through
the use of proper eye, skin, nose and
mouth protection. Such work may
require special precautions.
5SR 340, SR 420
English / USA
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.
!Warning!
An electrostatic charge may be created
in the extension tube and nozzle area
when applying dry materials (e.g. dusts)
with the dusting and spreading
attachment (special accessory). This is
especially true in low humidity
conditions. Check the label and/or
material safety data sheet for the
chemical you are applying. To reduce
the risk of severe or fatal injury, do not
use your mistblower to apply substances
that may create a combustible or
explosive dust cloud. For instance,
never use your mistblower to apply
sulfur or sulfur compounds, since they
may be highly explosive and have
relatively low melting and ignition points.
!Warning!
To reduce the risk of sparking when
applying any dry substance, make sure
that the discharge system (conductive
wire in the mistblower connected to a
metal chain) is completely and properly
mounted to the machine, and that the
discharge chain is making contact with
the ground. It is essential to follow the
fitting instructions supplied with the
dusting and spreading attachment.
HANDLING OF CHEMICALS
!Warning!
Chemicals can be harmful to individuals,
animals and the environment if
improperly used. In addition, some
chemicals that are caustic, corrosive or
poisonous should not be used in your
mistblowers.
Carefully read the labels on chemical
containers prior to use. Chemicals are
classified into categories of toxicity.
Pesticides regulated by the EPA, for
instance, use signal words to indicate
the product’s potential to make you sick.
“Caution“ appears on pesticides found to
be least harmful to humans. “Warning“
indicates a product that is more
poisonous than those in the “Caution“
group. Pesticides with the signal word
“Danger“ on the label are very
poisonous or irritating. They should be
used with extreme care. Finally,
pesticides labeled “Danger – Poison“
are for restricted use only and generally
must be used under the supervision of a
certified applicator. Each category will
have unique handling characteristics.
Familiarize yourself with the
characteristics for the category you are
using.
!Warning!
Mix only compatible pesticides. Wrong
mixtures can produce toxic fumes.
6
SR 340, SR 420
English / USA
When handling chemicals and when
spraying, make sure you are operating
in accordance with local, state, and
federal environmental protection rules
and guidelines. Do not spray in windy
conditions.To help protect the
environment, use only the
recommended dosage – do not overuse.
!Warning!
Do not eat, drink, or smoke while
handling chemicals or while you are
spraying. Never blow through nozzles,
valves, pipes or any other component by
mouth. Always handle chemicals in a
well ventilated area while wearing
appropriate protective clothing and
safety equipment. Do not store or
transport chemicals with food or
medicines, and never reuse a chemical
container for any other purpose.
Do not transfer spray materials to other
containers, especially food and/or drink
containers.
!Warning!
In case of accidental contact or ingestion
of chemicals or in case of contamination
of clothing, stop work and immediately
consult the chemical manufacturer’s
instructions. If in doubt as to what to do,
consult a poison control center or doctor
without delay. Have the product’s label
available to read to or show the persons
you consult.
Clean all chemical spills immediately.
Dispose of any residue in accordance
with state or federal laws and
regulations.
!Warning!
Keep chemicals out of reach of children,
other unauthorized people or animals.
When not in use, store chemicals in a
safe place. Follow the manufacturer’s
recommendations for proper storage.
THE USE OF THE POWER TOOL
Transporting the Power Tool
Always switch off the engine before
taking the machine off your back and
putting it down. Empty container 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 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.
7SR 340, SR 420
English / USA
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.
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
opening, the cap is not properly seated
and tightened and you must repeat the
above steps.
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.
8
SR 340, SR 420
English / USA
Filling the Container
!Warning!
Tighten all connections and check to be
sure the hose is securely attached and
in good condition. Keep the stop cock
closed.
Before using the power tool with
chemicals, fill it with fresh water to
assure that you have it properly
assembled and practice spraying. Also,
check for any leaks at this time. When
thoroughly familiar with the power tool
operation, follow normal operating
procedures.
Fill your power tool in well-ventilated
areas, outdoors.
!Warning!
Do not use:
– flammables in the mistblower, which
can explode causing serious or fatal
injury;
– caustic or corrosive materials in the
mistblower, which could result in
damage to the unit;
– liquids with a temperature above
120° F (50° C) to avoid scalding and
damage to the unit.
To fill the power tool, place it on a level
surface. To reduce the risk of
contaminating the surrounding
environment, be careful not to overfill the
container with chemical solution.
If you fill the container with a hose
attached to a central water supply, be
sure the end of the hose is out of the
solution to reduce the risk of backflow,
i.e. the chemicals being sucked into the
water supply in the case of a sudden
vacuum.
Calculate the correct amount of
chemical solution so that it is used up at
one time, with no extra solution left in the
tank.
!Warning!
Check for leakage while refilling and
during operation. A leak from the
container or a loose fitting could soak
your clothing and come into contact with
your skin.
Before Starting
!Warning!
Always check your power tool for proper
condition and operation before starting,
particularly the throttle trigger, setting
lever and stop switch. The throttle trigger
must move freely and always spring
back to the idle position. Never attempt
to modify the controls or safety devices.
!Warning!
To reduce the risk of leakage and skin
contact with chemicals, check that the
cap and all connections are tight, and be
sure the hose is securely attached and
in good condition. Keep the stop cock
closed.
!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, fuel mix,
grease or resin in order for you to
maintain a firm grip and properly control
your power tool.
9SR 340, SR 420
English / USA
!Warning!
To reduce the risk of injury from thrown
parts, check the fan housing for damage
(cracks, nicks, chipping). If any damage
is found, stop using the unit and contact
your STIHL dealer for repair.
Starting
Start the engine at least 10 feet
(3 meters) from the fueling spot,
outdoors only.
!Warning!
Your power tool is a one-person
machine. To reduce the risk of eye or
other injury from thrown objects, insure
that by-standers are at least 50 feet
(15 m) away during use. Stop operation
immediately if you are approached.
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!
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.
The assistance of another person may
be needed in placing the unit on your
back after starting. In order to reduce the
risk of injury to the assistant from thrown
objects, chemical spray/dust or from
contact with hot exhaust fumes, the
engine should be kept at idle speed
during this brief period, and your
assistant should not stand in the area of
the outlet nozzle or exhaust. Otherwise,
the unit should be started and operated
without assistance.
During Operation
Holding and controlling the power
tool
372BA019 KN
The mistblower is designed for singlehanded operation with the right hand on
the control handle. It should be carried
as a backpack with the straps of the
harness over both shoulders.
!Warning!
To reduce the risk of loss of control,
never carry the unit with the strap(s)
over one shoulder.
Wrap your fingers tightly around the
handle, keeping the control handle
cradled between your thumb and
forefinger. Keep your hand in this
position to have your machine under
control at all times.
10
SR 340, SR 420
English / USA
!Warning!
Adjust carrying harness to suit your size
before starting work.
In an emergency, you may slip out of the
harness and throw off the machine
quickly. Try slipping out of the harness a
number of times before using the
machine in order to become
accustomed to it. Do not throw off the
machine while practicing as it could
damage the machine.
!Warning!
In order to keep the container upright
and reduce the risk of spillage, do not
bend at the waist. Bend only at the
knees and support yourself as required
to ensure proper balance.
Remember that a mistblower filled with
liquid has a significant amount of weight.
Use caution when bending, leaning or
walking.
!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.
To reduce the risk of stumbling and loss
of control, do not walk backward while
operating the machine.
!Warning
To reduce the risk of injury from loss of
control, never work on a ladder, in a tree
or on any other insecure support.
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!
Inhalation of chemicals can cause
susceptible persons to have an allergic
or asthmatic reaction. Substantial or
repeated inhalation of certain chemicals
may cause respiratory disease, cancer,
birth defects or other reproductive harm.
Control the chemical spray/dust at the
source where possible. Use good work
practices, such as operating the unit so
that the wind or operating process does
not blow the chemical spray/dust back
on the operator. Follow the
recommendations of EPA/OSHA/
NIOSH and occupational and trade
associations with respect to proper
usage. When the inhalation of the
chemical spray/dust being applied
cannot be avoided, the operator and any
bystanders may need to wear a
respirator approved by NIOSH/MSHA
for the type of chemical encountered.
Consult the label of the chemical product
being used.
11SR 340, SR 420
English / USA
!Warning!
If you are unfamiliar with the risks
associated with the particular chemical
at issue, review the product label and/or
material safety data sheet for that
substance and/or consult the material
manufacturer/supplier. You may also
consult your employer, governmental
agencies such as the EPA, OSHA and
NIOSH and other sources on hazardous
materials. The state of California and
some other authorities, for instance,
have published lists of substances
known to cause cancer, reproductive
toxicity, etc.
Operating instructions
!Warning!
In the event of an emergency, switch off
the engine immediately – move the slide
control / stop switch to 0 or STOP.
!Warning!
Never spray in the direction of humans,
animals or property which might be
injured or damaged by spray formula.
Pay attention to the direction of the wind,
i.e., do not work against the wind. When
spraying, stand so that the wind does
not blow towards you or bystanders.
Keep children and pets away from areas
that have just been sprayed. After the
use of some chemicals, especially
agricultural pesticides, a notice must be
posted on the treated area that a
“Restricted Entry Interval“ (REI) is in
effect. See the product’s label and any
applicable governmental regulations.
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. Do not
spray on or near electrical installations.
!Warning!
To reduce the risk of personal injury, do
not direct air blast towards bystanders,
since the high pressure of the air flow
could injure eyes and could blow small
objects at great speed.
!Warning!
Always shut off the engine before
cleaning or servicing the unit or
replacing parts.
!Warning!
The blower fan between the air intake
and output openings rotates whenever
the engine is running.
Never insert any foreign object into the
air intake of the machine or into the
nozzle of the blower. It will damage the
fan wheel and may cause serious injury
to the operator or bystanders as a result
of the object or broken parts being
thrown out at high speed.
Do not place the blower on the ground
when operating at high speed, because
small objects such as sand, grass, dust,
etc. may be pulled into the air intake and
damage the fan wheel.
!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.
12
SR 340, SR 420
English / USA
!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.
After Finishing Work
Always wash thoroughly with soap and
water after spraying or handling
chemicals. Shower immediately, and
wash all protective clothing separately
from other items. Follow any additional
recommendations of the chemical
manufacturer.
Always clean dust and dirt off the power
tool.
!Warning!
Empty, rinse and clean container and
assembly after each use. This helps to
prevent the solution from crystallizing,
which could later cause clogging and
chemical damage to the unit. In addition;
residual chemicals may have
undesirable effects during subsequent
spraying with a different type of chemical
(e.g., residual herbicide may damage or
kill plants being sprayed with a
pesticide).
Disposal of contaminated rinse should
be in accordance with applicable
ordinances. Observe the precautionary
instructions of the chemical
manufacturer.
Do not store the mistblower with spray
solution in the container.
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 maintenance
chart near the end of the instruction
manual.
!Warning!
Always stop the engine and make sure
that the fan is stopped before doing any
maintenance or repair work or cleaning
the power tool.
13SR 340, SR 420
English / USA
Assembling the Machine
!Warning!
Do not attempt any maintenance or
repair work not described in your
instruction manual. Have such work
performed by your STIHL servicing
dealer only.
!Warning!
Use the specified spark plug and make
sure it and the ignition lead are always
clean and in good condition. Always
press spark plug boot snugly onto spark
plug terminal of the proper size. (Note: If
terminal has detachable SAE adapter
nut, it must be securely attached.) A
loose connection between spark plug
terminal and the ignition wire connector
in the boot may create arcing that could
ignite combustible fumes and cause a
fire.
!Warning!
Never test the ignition system with the
spark plug 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.
Tighten all nuts, bolts and screws,
except the carburetor adjustment
screws, after each use.
For any maintenance of the emission
control system please refer to the
maintenance chart and to the limited
warranty statement near the end of the
instruction manual.
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.
The throttle cable is already
connected and must not be kinked
during assembly.
Mounting the elbow
2
3
1
The combination wrench and carburetor
screwdriver are stowed on the underside
of the machine.
: Line up the stops on the elbow and
stub and push the elbow (1) into the
stub (2) as far as it will go.
: Fit the nut (3) in the hexagon recess
in the stub.
: Insert the screw in the nut from the
other side and tighten moderately –
the elbow must still turn.
372BA023 KN
14
SR 340, SR 420
English / USA
Mounting the extension tube
1
2
: Rotate the pleated hose (1) as far as
stop.
: Turn the control handle (2) so that it
is horizontal.
4
3
1
: Push the extension tube (3) into the
pleated hose (1) as far as it will go.
: The metering unit (4) must point in
the same direction as the control
handle.
5
372BA024 KN
: Tighten down the clamp screw (5)
(see “Adjusting the control handle”).
372BA025 KN
Fitting the liquid hose
2
1
372BA026 KN
: Secure liquid hose (1) from the
container to the pleated hose with
the retainer (2).
4
1
: Use hose clips (4) to secure hose
(1) and hose (3) to the stubs on the
stop cock.
: Close the stop cock (move lever to
vertical position).
: Fill up with water and check all hose
connections for leaks.
4
372BA027 KN
3
372BA028 KN
15SR 340, SR 420
English / USA
Harness
Adjusting the control handle
2
1
: Put the machine on your back.
: Loosen the clamp screw (1).
: Slide the control handle (2) along
the tube to the most comfortable
position.
: Tighten down the clamp screw (1)
firmly.
Adjusting the Harness
372BA029 KN
: Pull the ends of the straps
downward to tighten the harness.
Loosening the Harness
: Lift the tabs of the sliding adjusters.
: Adjust the straps so that the
backplate is held firmly and
comfortably against your back.
Throwing Off Backpack
373BA003 KN
Before using the machine, make
yourself familiar with how to release and
throw off the backpack.
In an emergency, quickly throw the
machine off your back as follows:
: Open the quick-release fastener on
the waist belt (special accessory).
: Open the strap hook on the
backplate by snapping it forwards
(arrow).
: Throw the machine to the rear.
373BA004 KN
16
SR 340, SR 420
Fuel
English / USA
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.
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
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.
Oil (STIHL 50:1 or
equivalent high-quality oils)
17SR 340, SR 420
English / USA
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 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.
After fueling, tighten fuel cap
as securely as possible by hand.
373BA030 KN
Change the fuel pick up body
every year.
Before storing your machine for a long
period, drain and clean the fuel tank and
run engine until carburetor is dry.
Information
Before You Start
With the engine stopped and before
starting, check the air intakes
between the backplate and
powerhead for blockages and clean
if necessary.
A protective screen is available as a
special accessory to keep the air
intakes clear.
The throttle cable disconnects itself from
the throttle trigger if the engine is not
shut off in the idle position.
The throttle cable reconnects itself
automatically when the setting lever is
moved to the idle position.
373BA007 KN
373BA037 KN
18
: Move the setting lever to the idle
position.
SR 340, SR 420
Starting / Stopping
the Engine
1
English / USA
2
: Observe safety precautions – see
chapter on “Safety Precautions and
Working Techniques”.
: Slide the stop switch (1) to #
: Move the setting lever (2) to the
center position – this is the
starting throttle position
The setting lever can be used to select
any throttle opening between idle speed
(lower stop) and full throttle (upper stop).
Set the lever to the idle position before
switching off the engine.
373BA008 KN
373BA009 KN
Before starting
: Move stop cock lever (3) to upright
position.
373BA010 KN373BA011 KN
: If the engine is cold, turn the choke
knob to g
: If the engine is warm, turn the
choke lever to e
Also use this position if the engine
has been running but is still cold.
19SR 340, SR 420
English / USA
: 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 the starter rope out all
the way as 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.
: Put the unit on the ground. Check
that bystanders are well clear of the
general work area and the nozzle.
: Make sure you have a firm footing:
Hold the unit with your left hand on
the housing and put one foot against
the base plate to prevent it slipping.
20
373BA012 KN
373BA013 KN
When engine begins to fire:
: If engine is cold:
Turn choke knob to e and continue
cranking until engine runs.
: If engine is warm:
Continue cranking until engine runs.
SR 340, SR 420
English / USA
: Fit the spark plug and reconnect the
spark plug boot.
: Move the stop switch to #
2
: Turn the choke knob to e
even if the engine is cold.
: Now start the engine.
1
As soon as engine runs:
: Move the setting lever (2) to the
lower stop so that the engine settles
down to idle speed.
To shut down the engine:
: Move the stop switch (1) to 0 or
STOP.
At very low outside temperatures:
Allow engine to warm up
As soon as engine runs:
: Move the setting lever to the lower
stop – the engine settles down to
idle speed.
: Open throttle slightly – warm up
engine for a short period.
373BA014 KN
373BA015 KN
If the engine does not start:
If you did not turn the choke knob to e
quickly enough after the engine began to
fire, the combustion chamber is flooded.
: Pull off the spark plug boot.
: Unscrew and dry off the spark plug.
: Move the stop switch to 0 or STOP.
: Open the throttle wide.
: Pull the starter rope several times to
clear the combustion chamber.
Fuel tank run until dry and then
refueled
: Pull the starter rope several times to
prime the fuel line.
373BA016 KN
21SR 340, SR 420
English / USA
Calculating Required
Quantity of Solution
Step 1:
Determine surface area (m2)
In the case of ground crops, multiply the
length of the field by its width.
The surface area of high-growing plants
is calculated approximately by
multiplying the length of the rows by the
average height of the foliage. The result
is multiplied by the number of rows and
then by two if both sides have to be
treated.
The area in hectares is obtained by
dividing the number of square meters by
10,000.
Example:
A field 120 meters long and 20 meters
wide has to be treated with a pesticide.
Area:
120 m x 30 m = 3,600 m
2
3,600 / 10,000 = 0.36 ha
Step 2:
Determine quantity of active
ingredient
Refer to the instructions supplied with
the active ingredient to determine:
: Required quantity of active
ingredient for 1 hectare (ha) and the
: concentration of active ingredient
(mix ratio)
Multiply the required quantity of active
ingredient for 1 ha by the area
determined in Step 1. The result is the
quantity of active ingredient required for
the area to be treated.
Example:
According to the maker’s instructions,
0.4 liters of active ingredient are
required per hectare to obtain a
concentration of 0.1%.
Quantity of active ingredient:
0.4 (l/ha) x 0.36 (ha) = 0.144 l
Step 3:
Determine quantity of solution
The required quantity of solution is
calculated as follows:
T
W
–––– x 100 = T
K
B
Where:
TW = Quantity of active ingredient in l
K = Concentration in %
T
= Required quantity of solution in l
B
Example:
In Step 2 the quantity of active ingredient
required was calculated to be 0.144 l.
According to the maker’s instructions,
the concentration is 0.1%.
Quantity of solution:
0.144 l
––––– x 100 = 144 l
0.1%
22
SR 340, SR 420
Metering Unit
English / USA
Step 4:
Determine walking speed
Carry out a trial run with the machine
fueled and the container filled with water.
Operate the spray tube (swing it back
and forth) as it will be during the real run
described below. Determine the
distance walked in one minute.
Also use the trial run to check the
selected working width. In the case of
low-growing crops, the best working
width is 4-5 m. The working width should
be marked with stakes.
Dividing the distance in meters by the
time in minutes gives you the walking
speed in meters per minute (m/min).
Example:
The distance covered in one minute is
10 meters.
Walking speed:
10 m
––––– = 10 m/min
1min
Step 5:
Determine discharge rate
The setting of the metering knob is
calculated as follows:
V
(l) x vb (m/min) x b(m)
a
–––––––––––––––––––––– = V
A (m
2
)
(l/min)
c
Va= Quantity of solution
v
= Walking speed
b
Vc= Discharge rate
b = Working width
A = Area
Example:
The values determined in Steps 1-4 and
a working width of 4 m produce the
following discharge rate (setting of
metering knob):
144 l x 10 (m/min) x 4 m
–––––––––––––––––––– = 1.6 l/min
3,600 m
2
: The stop cock (1) is closed when the
lever is upright.
: The stop cock (1) is open when the
lever is parallel to the hose.
: Adjust the discharge rate with the
metering knob – not the stop cock.
Hectares (ha) have to be converted into
m2 (ha x 10,000 = m2).
23SR 340, SR 420
English / USA
2
1
3
6
2
4
5
4
3
: The discharge rate can be infinitely
varied by turning the metering knob
(2) on the nozzle (3).
: Position 1 = minimum flow rate
: Position 6 = maximum flow rate
The required number on the metering
knob must be lined up with the molded
lug (4) under the knob.
Discharge rate without pressure
1)
pump
Knob
position
Discharge rate (l/min)
SR 340 SR 420
10.080.12
20.410.44
30.850.86
372BA005 KN
41.281.27
51.591.58
61.811.81
Discharge rate without pressure
pump, with ULV nozzle
1)
ULV nozzle Discharge rate (l/min)
SR 340 SR 420
0.5 0.03 0.03
0.65 0.06 0.07
0.8 0.10 0.10
1)
Table shows the mean discharge
rates at full throttle with spray tube at
0° and 30° to horizontal.
Discharge rate with pressure pump
(special accessory)
Metering
nozzle
Discharge rate (l/min)
SR 340 SR 420
1.0 0.57 0.64
1.6 1.70 1.88
2.0 2.90 3.13
Discharge rate with pressure pump
(special accessory) and ULV nozzle
ULV nozzle Discharge rate (l/min)
SR 340 SR 420
0.5 0.10 0.10
0.65 0.16 0.20
0.8 0.28 0.42
24
SR 340, SR 420
English / USA
Checking metering unit
: Place the machine on the ground.
: Remove the baffle screen and
pressure pump.
: Fill the container with water up to 10
liter mark.
: Set the metering knob to “6”
: Start the machine.
: Hold the spray tube horizontally, run
the engine at full throttle, spray the
contents of the container down to
the 5 liter mark and note the time
taken.
The time required to spray 5 liters fluid
should be between 140 and 170
seconds.
In case of deviations:
: Check the metering unit for
contamination and clean it if
necessary.
: Check engine setting and correct if
necessary.
Filling the Container
: Stand the machine on a level
surface.
: Close the stop cock.
: Fill up with thoroughly mixed spray
solution – do not exceed maximum
level of 13 liters (arrow).
1
Mistblowing
: Always use full throttle when
mistblowing.
: Stop cock must be fully open while
mistbllowing – do not vary the flow
rate via the stop cock.
Different baffle screens enable the
shape of the spray jet to be varied.
Tapered baffle screen
372BA029 KN
372BA006 KN372BA007 KN
Spray is finely atomized – short, broad
and dense spray pattern.
Deflector baffle screen
372BA021 KN
If no there is no improvement, contact
your dealer for assistance.
: The gasket (1) in the cap must
always be lubricated with grease.
: Fit the cap and screw it down tightly.
Diverts spray jet at an angle – for underleaf treatment of low-growing crops.
25SR 340, SR 420
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