Stihl Br 420 C Manual

							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.
STIHL BR 340, 420
BA_BR340_30_U_D3.book  Seite 0  Donnerstag, 27. März 2003  11:49 11 
						

							1
BR 340, BR 340 L, BR 420, BR 420 C English / USA
BA_SE_003_004_01_09.fm
Printed on chlorine-free paper.
Printing inks contain vegetable oils; paper can be recycled.
© ANDREAS STIHL AG & Co. KG, 2005 
0458 373 3021 B
. M2. L5.  CP . Prin ted  in US A 
STIHlContentsGuide to Using this Manual  ..............  2
Safety Precautions  ...........................  3
Assembling the Blower  ...................  12
Fuel ................................................  14
Fueling ............................................  15
Information Before You Start  ..........  16
Starting / Stopping the Engine  ........  16
Operating Instructions  ....................  19
Cleaning the Air Filter  .....................  19
Motor Management  ........................  20
Adjusting the Carburetor  ................  20
Catalytic Converter  .........................  22
Checking the Spark Plug  ................  22
Spark Arresting Screen in Muffler  ...  23
Replacing Starter Rope 
and Rewind Spring  .........................  24
Storing the Machine  ........................  27
Maintenance Chart  .........................  28
Parts and Controls  .... ......................  29
Specifications .................................  31
Special Accessories  .......................  32
Maintenance and Repairs ...............  32
STIHL Incorporated Federal 
and California Emission Control 
Warranty Statement  ........................  33
Trademarks ....................................  35 Allow only persons who understand this 
Manual to operate your blower.
To receive maximum performance and 
satisfaction from your STIHL blower, it is 
important that you read and understand 
the maintenance and safety precautions,
 
starting on page 3, before using your 
blower. 
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 blower is a high-speed tool, 
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. 
STIHLs 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 blower differs from 
those described in this Manual, please 
contact your STIHL dealer for 
information and assistance. 
						

							2 English / USA
BR 340, BR 340 L, BR 420, BR 420 CPictogramsAll the pictograms attached to the 
machine are shown and explained in  
this manual.
The operating and handling instructions 
are supported by illustrations.Symbols in textThe 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 under-
standing 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 featuresThis 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 improvementsSTIHL’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.
Guide to Using this Manual 
						

							3 BR 340, BR 340 L, BR 420, BR 420 CEnglish / USA
Warning!
The use of any blower 
may be dangerous. It is 
important that you read, 
fully understand and 
observe the following safety 
precautions.
!
Warning!
Reread the owner`s 
manual and the safety 
instructions peri-
odically.
Do not lend or rent your machine without 
the owner`s manual.
Be sure that anyone using your unit 
understands the information contained 
in this manual.
!
Warning!
Careless or improper use of the machine 
may cause serious injury. Have your 
STIHL Dealer show you how to operate 
your blower. Observe all applicable 
local safety regulations, standards and 
ordinances.
!
Warning!
Minors should never be allowed to use a 
blower. Bystanders, especially children, 
and animals should not be allowed in the 
area where a machine is in use.
Never let the unit run unattended.Most of these safety precautions and 
warnings apply to the use of all STIHL 
blowers. Different models may have 
different parts and controls.
See the appropriate section of your 
owner`s manual for a description of the 
controls and function of the parts of your 
machine.
Safe use of a blower involves
1. the operator
2. the blower 
3. the use of the blower.
THE OPERATORPhysical 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 a 
blower when you are fatigued.
Be alert - if you get tired while operating 
your machine, take a break. Tiredness 
may result in loss of control. Working 
with any blower can be strenuous.  If you 
have any condition that might be 
aggra
vated by strenuous work, check 
with your doctor before operating the 
machine.Your STIHL blower is equipped with an 
antivibration system (AV). The AV 
system is designed to reduce the 
transmission of engine vibrations to the 
operators body. An AV system is 
recommended for those operators who 
use blowers on a regular or sustained 
basis.
Keep the AV system well maintained. A 
blower with loose components or with 
damaged or worn AV buffers will tend to 
have higher vibration levels.
!
Warning!
The ignition system of your 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 pacemaker should consult 
their physician and the pacemaker 
manufacturer before operating this tool.
Safety Precautions 
						

							4 English / USA
BR 340, BR 340 L, BR 420, BR 420 C Proper Clothing !
Warning!
To reduce the risk of injury, the operator 
should wear proper protective apparel.
Clothing must be sturdy and snug-fitting, 
but allow complete freedom of move-
ment.
!
Warning!
Avoid loose-fitting jackets, 
flared or cuffed pants, 
scarfs, unconfined long 
hair or anything that could 
be drawn into the air 
intake. 
Use of gloves when 
working with the blower is 
recommended. 
Good footing is most 
important. Wear sturdy 
shoes with nonslip soles.
!
Warning!
To reduce the risk of injury associated 
with the inhalation of dust, use an 
appropriate dust respirator for the 
material being blown.
!
Warning!
Use of this product can generate dust, 
mists, and fumes containing chemicals 
known to cause respiratory disease, 
cancer, birth defects, or other reproduc-
tive harm. If you are unfamiliar with the 
risks associated with the particular dust, 
mists or fumes at issue, consult your 
employer, governmental agencies such 
as OSHA and NIOSH and other sources 
on hazardous materials. If the substance 
being blown or vacuumed is a commer-
cial substance, review the material 
safety data sheet for that substance and 
/ or consult the material manufacturer / 
supplier. The state of California and 
some other authorities, for instance, 
have published lists of substances 
known to cause cancer, reproductive 
toxicity, etc.
Control dust, mist and fumes at the 
source where possible. In this regard 
use good work practices and follow the 
recommendations of OSHA / NIOSH 
and occupational and trade associa-
tions. When the inhalation of toxic dust, 
mists and fumes cannot be eliminated, 
the operator and any bystanders should 
always wear a respirator approved by 
NIOSH / MSHA for the substance at 
issue.
!
Warning!
Dust with silica in its composition may 
contain crystalline silica. Silica is a basic 
component of sand, quartz, brick, clay, 
granite and numerous other minerals 
and rocks, including masonry and con-
crete products. 
Repeated and / or sub-stantial inhalation 
of airborne crystalline silica can cause 
serious or fatal respira-tory disease, 
including silicosis. In addi-tion, the state 
of California and some other authorities 
have listed respirable crystalline silica as 
a substance known to cause cancer. 
When encountering such materials, 
always follow the re-spiratory 
precautions mentioned above.
!
Warning!
Breathing asbestos dust is dangerous 
and can cause severe or fatal injury, re-
spiratory illness or cancer. The use and 
disposal of asbestos containing 
products 
have been strictly regulated by OSHA 
and the Environmental Protection 
Agency. Do not blow or disturb asbestos 
or asbestos containing products, such 
as asbestos insulation. If you have any 
reason to believe that you might be 
disturbing asbestos, immediately 
contact 
your employer or a local OSHA 
representative. 
						

							5 BR 340, BR 340 L, BR 420, BR 420 CEnglish / USA
!
Warning!
Proper eye protection is a must. Even 
though the discharge is directed away 
from the operator, ricochets and bounce 
backs can occur during blower 
operations.
Never operate a blower 
unless wearing goggles
or properly fitted safety 
glasses with adequate
 top and side protection 
which comply with 
ANSI Z 87.1 (or your applicable national 
standard).
Fellow workers must also wear personal 
protective equipment.
!
Warning!
Blower 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 regulary.
THE BLOWER For illustrations and definitions of the 
blower parts see the chapter on Parts 
and Controls!!
Warning! 
Never modify a blower in any way. Only 
attachments supplied by STIHL or 
expressly approved by STIHL for use 
with the specific STIHL blower models 
are authorized. Although certain 
unauthorized attachment are useable for 
the STIHL blower, their use may be 
extremely dangerous.
THE USE OF THE BLOWER Tr a n s p o r t
Always turn off the engine before taking 
the machine off your back and putting it 
down. When transporting your unit in a 
vehicle, properly secure it to prevent 
turnover, fuel spillage and damage to the 
machine.
Adjust carrying harness to suit your size 
before starting work.!
Warning!
Before starting work, always inspect the 
rubber buffers which connect the engine 
to the pack frame. If the buffers are torn 
or damaged, they should be replaced by 
your STIHL dealer. Failure of one or 
more buffers may cause the engine or 
fuel tank to hit or rub against other parts, 
and may lead to serious injury from 
increased vibrations or from fire as the 
result of fuel leakage.
Fuel
This STIHL unit uses an oil-gasoline 
mixture for fuel (see the chapter on 
Fuel of your owner`s manual).  
						

							6 English / USA
BR 340, BR 340 L, BR 420, BR 420 C!
Warning!
Gasoline is an extremely 
flammable fuel. If spilled 
or ignited by a spark or 
other ignition source, it 
can cause fire and serious 
burn injury or property 
damage.
!
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.
Use extreme caution when handling 
gasoline or fuel mix. 
Do not smoke or bring any fire or flame 
near the fuel.Fueling instructions
Fuel your machine in well-ventilated 
areas, outdoors only. Always shut off the 
engine and allow it to cool before 
refueling. Relieve fuel tank pressure by 
loosening fuel cap slowly. Never remove 
fuel filler cap while engine is running.
Select bare ground for fueling and move 
at least 10 feet (3 m) from the fueling 
spot before starting the engine. Always 
tighten fuel filler cap securely after 
fueling. Wipe off any spilled fuel before 
starting your blower and check for 
leakage.
!
Warning!
Check for fuel leakage while refueling 
and during operation. If fuel or oil 
leakage is found, do not start or run the 
engine until leak is fixed and spilled fuel 
has been wiped away. Take care not to 
get fuel on your clothing. If this happens, 
change your clothing immediately.
Always store gasoline in approved 
container.
!
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.
!
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. 
						

							7 BR 340, BR 340 L, BR 420, BR 420 CEnglish / USA
Before Starting 
!
Warning!
Never operate your machine if it is 
damaged, improperly adjusted or not 
completely and securely assembled.
You should always inspect your unit 
before starting it. Make sure the controls 
and safety devices are working properly.
!
Warning!
To reduce the risk of injury from thrown 
parts, check your fanwheel and fan 
housing for damage (cracks, nicks, 
chipping). If any damage is found, stop 
using the unit and contact your STIHL 
dealer for repair.
:Throttle trigger must move freely 
and spring back to idle position 
when released.
:Stop switch must move easily to  $ 
:Tightness of spark plug boot - if boot 
is loose, sparks may occur and 
ignite fuel vapor!
:Condition of fanwheel and fan 
housing.Starting
!
Warning!
Your blower 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 (15m) away 
during use. 
Stop the operation immediately if you 
are approached.
For specific starting instructions, see the 
appropriate section of your owner`s 
manual. Place the machine on firm 
ground or other solid surface in an open 
area. Maintain good balance and secure 
footing.
!
Warning!
When you pull the starter grip, don`t 
wrap the starter rope around your hand. 
Do not allow the grip to snap back, but 
guide the starter rope slowly back to 
permit the rope to rewind properly. 
Failure to follow this procedure may 
result in injury to 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 or from contact with 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. 
						

							8 English / USA
BR 340, BR 340 L, BR 420, BR 420 C Muffler and Catalytic Converter!
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 or burn injury, 
let the unit cool down before refueling 
your power tool after use.
!
Warning!
Never disassemble or modify your 
muffler. The muffler could be damaged 
and cause an increase in heat radiation 
or sparks, thereby increasing the risk 
of fire or burn injury. You may also 
permanently damage the engine. Have 
your muffler serviced and repaired by 
your STIHL servicing dealer only.
!
Warning!
To reduce the risk of fire or burn injury, 
keep the area around the muffler clean. 
Remove all debris such as pine needles, 
branches or leaves.
!
Warning!
Some STIHL blower 
models are equipped with 
a catalytic converter, 
which is designed to 
reduce the exhaust 
emissions of the engine 
by a chemical process in the muffler. 
Due to this process, the muffler does not 
cool down as rapidly as conventional 
mufflers when the engine returns to idle 
or is shut off. To reduce the risk of fire 
and burn injuries, the following specific 
safety precautions must be observed.
!
Warning!
Since a muffler with a catalytic converter 
cools down less rapidly than 
conventional mufflers, always set your 
backpack blower 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. 
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!
An improperly mounted or damaged 
cylinder housing or a damaged/
deformed muffler shell may interfere 
with the cooling effect 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. Your muffler is 
furnished with a screen designed to 
reduce the risk of fire from the emission 
of hot particles. Due to the heat from the 
catalytic reaction, this screen on a 
catalytic converter 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.
      
        
         
 
         
    
						

							9 BR 340, BR 340 L, BR 420, BR 420 CEnglish / USA
Working instructions
Work carefully. 
When working with the blower, always 
wear it on your back using the carrying 
harness. 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. 
Make sure your control handle (and grip 
for vacuum attachment) are in good 
condition and free of moisture, pitch, oil 
or grease.
Operate the blower under good visibility 
and daylight conditions only.
!
Warning!
Your blower produces 
poisonous exhaust fumes 
as soon as the combus-
tible engine is running. 
These gases (e.g. carbon 
monoxide) may be color-
less and odorless. To reduce the risk of 
serious or fatal injury from breathing 
toxic fumes, never start or run the blower 
indoors or in poorly ventilated locations. 
Ensure proper ventilation when working 
in trenches or other confined areas.
Keep the space behind and beside the 
engine clear at all times to allow for the 
escape of hot and toxic exhaust fumes. 
!
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.
To reduce the risk of stumbling and loss 
of control,do not walk backward while 
operating the machine.
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 with it.
Do not throw off the machine while 
practising as it could damage the 
machine.
Pay attention to the direction of the wind, 
i.e., do not work against the wind.
353BA039 KN