Stihl Br 420 C Manual

							10 English / USA
BR 340, BR 340 L, BR 420, BR 420 CUsing the BlowerThe blower is designed for single-
handed operation. It is carried as a 
backpack and operated with the right 
hand on the control handle.
The powerful ground-level airstream can 
be aimed highly accurately and 
effectively. It enables the operator to 
quickly blow-sweep large areas. 
The blower may be used only for the 
operations described in your manual.
The blower can be used for clearing 
leaves, grass, paper, dust and light snow 
in yards, gardens, sports stadiums, 
parks, driveways and parking lots. It is 
also suitable for clearing forest paths.
Other applications are blowing out 
pipes, drains, gutters and your carport.
Working techniquesTo minimize blowing time, use rakes and 
brooms to loosen debris before blowing.
Recommended working techniques to 
minimize airborne debris and pollution:
:In dusty conditions, slightly dampen 
surfaces.
:Use the full blower nozzle extension 
so the air stream can work close to 
the ground.
:Do not direct debris at people, 
children, pets, at open windows or 
freshly-washed cars. Blow debris 
safely away.
:After using blowers, CLEAN UP. 
Dispose of debris in trash 
receptacles. Do not blow debris 
onto neighboring properties.Recommended working techniques to 
minimize noise:
:Operate power equipment only at 
reasonable hours - not early in the 
morning, late at night or during the 
noon-break when people might be 
disturbed. Comply with times listed 
in local ordinances. Usual 
recommendations are 9:00 a.m. to 
12:00 a.m. and 03:00 p.m. to 5:00 
p.m. on workdays for professionals. 
Special considerations should be 
given to neighbors on weekends. 
:Fewer engines mean less noise; 
therefore use only one piece of 
power equipment at a time, when 
possible.
:Operate power blowers at the 
lowest possible throttle speed to do 
the job.
:Check your equipment before 
operation, especially the muffler, air 
intakes and air filters.
Conserve water by using power blowers 
instead of hoses for those lawn and 
garden applications where a blower can 
be properly used, such as cleaning 
patios or porches. 
						

							11 BR 340, BR 340 L, BR 420, BR 420 CEnglish / USA
Using the Vacuum Attachment
(special accessory) 
The vacuum is designed to pick up dry 
material such as leaves, grass, small 
twigs and bits of paper.
!
Warning!
To reduce the risk of 
personal injury from fire 
and explosion, never 
attempt to pick up hot or 
burning substances (e.g. 
smoldering ashes, 
glowing cigarettes)
or combustible fluids (e.g. 
gasoline, paint thinners).
MAINTENANCE, REPAIR AND
STORINGMaintenance, replacement, or repair 
of the emission control devices and 
systems may be performed by any 
nonroad engine repair establishment 
or individual. However if you claim 
warranty for a component which has 
not been serviced or maintained pro-
perly or if nonapproved replacement 
parts were used, STIHL may deny 
warranty.
Use only identical STIHL replacement 
parts for maintenance and repair. Use of 
parts manufactured by others may 
cause serious or fatal injury.
Follow the maintenance and repair 
instructions in the appropriate section of 
your owners manual. Refer to the 
maintenance chart at the last pages of 
this manual.!
Warning!
Always stop the engine and make sure 
that the fan is stopped before doing any 
maintenance or repair work or cleaning 
the blower. Do not attempt any mainten-
ance or repair work not described in your 
owners manual. Have such work 
performed at your STIHL servicing 
dealer only.
Check fuel filler cap for leaks at regular 
intervals. Use the specified spark plug 
and make sure it and the ignition lead 
are always in good condition.Tighten all nuts, bolts and screws except 
the carburetor adjustment screws after 
each use.
!
Warning!
A worn or damaged muffler is a fire 
hazard and may cause loss of hearing. 
Check to see that the muffler is in good 
condition. The blower must not be 
opera-
ted if the muffler is not functioning pro-
perly or has been removed. 
Remember that the risk of forest fires is 
greater in hot weather. Use the spark 
arresting muffler supplied with the unit. 
Never touch a hot muffler or burn will 
result.
!
Warning!
In order to reduce the risk of fire, do not 
modify or remove any part of the muffler 
or spark arrestor.
Keep spark plug and wire connection 
tight and clean. The spark plug electrode 
gap should be checked with a feeler 
gauge at least every 50 operating hours 
and reset if necessary. Fit a new spark 
plug if the electrodes are badly pitted.
For any maintenance please refer to the 
maintenance chart and to the warranty 
statement near the end of this manual.
Store blower in a dry, high or locked 
location and out of reach of children.
Before storing for longer than a few 
days, always empty the fuel tank. 
						

							12 English / USA
BR 340, BR 340 L, BR 420, BR 420 CMounting the ElbowA combination wrench and carburetor 
screwdriver are stowed on the underside 
of the blower.
The throttle cable is already 
connected and must not be kinked 
during assembly.
:Push the elbow (1) into the stub (2) 
as far as it will go – the stops on the 
elbow and fan housing stub must 
line up.
: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. :Secure the throttle cable (4) to the 
pleated hose with the retainer (5).
Mounting Blower Tube with 
Straight Nozzle*
Operate the machine only with the 
blower tube and nozzle properly 
mounted.
:Push the blower tube (6) into the 
pleated hose (7).
:Push the nozzle (8) onto the blower 
tube (6) to position ’a’ (long) or ’b’ 
(short), as far as lug (9), and rotate 
it in the direction of the arrow 
(clockwise) to lock.
* see Guide to Using this Manual:Rotate the pleated hose (7) 
counterclockwise as far as stop and 
leave it in that position.
:Turn the control handle (10) 
counterclockwise to the horizontal 
position and tighten down the clamp 
screw (11).
Assembling the Blower
353BA002 KN
2
3
1
373BA033 KN
74
8 10
6 11 5
9
a
b 
						

							13 BR 340, BR 340 L, BR 420, BR 420 CEnglish / USA
Mounting Blower Tube with 
Curved Nozzle*
Operate the machine only with both 
blower tubes properly mounted.
: Push the blower tube (6) into the 
pleated hose (7).
:Push blower tube (12) onto blower 
tube (6) to position ’a’ (long) or ’b’ 
(short), as far as lug (9), and rotate 
it in the direction of the arrow 
(clockwise) to lock.
:Fit the nozzle (13) on the end of the 
blower tube (12) and rotate it 
clockwise to engage the bayonet 
coupling.
* see Guide to Using this Manual:  Rotate the pleated hose (7) 
counterclockwise as far as stop and 
leave it in that position.
:Turn the control handle (10) 
counterclockwise to the horizontal 
position. 
:Rotate the complete blower tube 
assembly until the nozzle discharge 
opening points in the same direction 
as the control handle.
:Tighten down the clamp screw (11).
Adjusting the Control Handle:Put the unit on your back.
:Loosen the clamp screw (11).
:Slide the control handle (10) along 
the pleated hose to the most 
comfortable position.
:Tighten down  the clamp screw (11).
373BA039 KN
7
12 10
6 119
a
b
13
1110
373BA002 KN 
						

							14 English / USA
BR 340, BR 340 L, BR 420, BR 420 CAdjusting the Harness Straps:Pull the ends of the straps 
downward to tighten the harness.Loosening the Harness Straps:Lift the tabs of the two sliding 
adjusters.
:Adjust the straps so that the 
backplate is held firmly and 
comfortably against your back.This engine is certified to operate on 
unleaded gasoline and the STIHL two-
stroke engine oil at a mix ratio of 50:1.
Your two-stroke engine requires a 
mixture of high-quality 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 (two-
stroke water cooled) mix oils or other 
mix oils that state they are for use in both 
water cooled and air cooled engines 
(e.g., outboard motors, snowmobiles, 
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.
373BA003 KN373BA004 KN
Fuel 
						

							15 BR 340, BR 340 L, BR 420, BR 420 CEnglish / USA
Fuel mix ages
Only mix sufficient fuel for a few days 
work, not to exceed 3 months of storage. 
Store in approved fuel-canisters only. 
When mixing, pour oil into the canister 
first, and then add gasoline. Close the 
canister and shake it vigorously by hand 
to ensure proper mixing of the oil with 
the fuel.       
Dispose of empty mixing-oil canisters 
only at authorized disposal locations.Before fueling, clean the filler cap and 
the area around it to ensure that no dirt 
falls into the tank.
Always thoroughly shake the mixture in 
the canister before fueling your 
machine.
In order to reduce the risk of burns 
or other personal injury from 
escaping gas vapor and fumes, 
remove the fuel filler cap carefully 
so as to allow any pressure build-up 
in the tank to release slowly.
After fueling, tighten fuel cap 
as securely as possible by hand. 
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. Gaso-
lineOil (STIHL 50:1 or 
equivalent high-quality oils)
US gal. US fl.oz
12.6
2 1/2 6.4
5 12.8
Fueling
373BA030 KN
373BA007 KN 
						

							16 English / USA
BR 340, BR 340 L, BR 420, BR 420 C 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.
Only machines with catalytic 
converter
:Move the setting lever to idle 
position.
Machines with a catalytic converter must 
always be switched off with the setting 
lever in the idle position because the 
throttle cable will otherwise disconnect 
itself from the throttle trigger. 
The throttle cable reconnects itself 
automatically when the setting lever is 
moved to the idle position.:Observe safety precautions – see 
chapter “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
Note:
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 idle position before 
switching off the engine.: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.Information 
Before You Start
373BA037 KN
Starting / Stopping 
the Engine
373BA008 KN
1
373BA009 KN
2
373BA010 KN373BA011 KN 
						

							17 BR 340, BR 340 L, BR 420, BR 420 CEnglish / USA
: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.:Pull the starter grip slowly with your 
right hand until you feel it engage 
and 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.
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. 
373BA012 KN
373BA013 KN 
						

							18 English / USA
BR 340, BR 340 L, BR 420, BR 420 C 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:
:Slide the stop switch (1) to $ 
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.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.
:Set the stop switch to 0 
:Open the throttle fully.
:Pull the starter rope several times to 
clear the combustion chamber.:Fit the spark plug and reconnect the 
spark plug boot.
:Move the stop switch to # 
:Turn the choke knob to e 
even if the engine is cold.
:Now start the engine.
Fuel tank run until dry and then 
refueled
:Pull the starter rope several times to 
prime the fuel line.
373BA014 KN
2
1
373BA015 KN
373BA016 KN 
						

							19 BR 340, BR 340 L, BR 420, BR 420 CEnglish / USA
During break-in period
A factory new machine should not be run 
at high revs (full throttle off load) for the 
first three tank fillings. This avoids 
unnecessary high loads during the 
break-in period. As all moving parts 
have to bed in during the break-in 
period, the frictional resistances in the 
engine are greater during this period. 
The engine develops its maximum 
power after about 5 to 15 tank fillings.
During operation
After a long period of full-throttle 
operation, allow engine to run for a while 
at idle speed so that the heat in the 
engine can be dissipated by flow of 
cooling air. This protects engine-
mounted components (ignition, 
carburetor) from thermal overload.
After finishing work
Wait for engine to cool down. Drain the 
fuel tank. Store the machine in a dry 
place. Check tightness of nuts and 
screws (not adjusting screws) at regular 
intervals and retighten as necessary.Dirty air filters reduce engine power 
increase fuel consumption and make 
starting more difficult.
If there is a noticeable loss of engine 
power
:Turn choke knob to g
:Release the screws (1) and pull 
off the filter cover (2).:Remove the main filter (3) from the 
cover and inspect it –
if it is dirty or damaged, fit a new 
one.
:Take the prefilter (4) out of the filter 
cover.
:Make sure the prefilter is dry – 
knock it out on the palm of your 
hand or blow out with compressed 
air. 
:Always replace a damaged prefilter.
Note:
Always install a new prefilter when 
you change the main filter.
Operating InstructionsCleaning the Air Filter
1
373BA017 KN
2
1
373BA018 KN
3
45