Stihl Br 420 C Manual

20 English / USA
BR 340, BR 340 L, BR 420, BR 420 C :Clean the filter cover and filter 
chamber.
:Install the main filter and prefilter 
elements in the filter cover.
:Fit the cover on the filter base (5) 
and tighten it down firmly.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.
General InformationThe carburetor comes from the factory 
with a...

21 BR 340, BR 340 L, BR 420, BR 420 CEnglish / USA
Standard Setting:Shut off the engine.
:Turn the high speed screw (H) and 
low speed screw (L) counter-
clockwise as far as stop (max. 
1/4 
turn).
Adjusting Idle SpeedEngine stops while idling
:Carry out standard setting on the 
low speed screw.
:Turn idle speed screw (LA) 
clockwise until the engine runs 
smoothly.
Erratic idling behavior, poor 
acceleration
:Carry out standard setting on the 
low speed screw. 
:Turn low speed screw (L)...

22 English / USA
BR 340, BR 340 L, BR 420, BR 420 C Units with a catalytic converter* may 
only be operated with unleaded 
gasoline and STIHL two cycle engine 
oil or equivalent quality two cycle engine 
oils in a mix ratio of 50:1 (see chapter 
“Fuel”).
The catalylic converter in the muffler 
reduces noxious emissions in the 
exhaust gas.
Correct adjustment of the carburetor (if 
adjustable) and observance of the 
specified mix ratio of gasoline and two 
cycle engine oil are essential to 
minimize...

23 BR 340, BR 340 L, BR 420, BR 420 CEnglish / USA
To reduce the risk of fire and burn 
injury, use only spark plugs 
authorized by STIHL. Always press 
spark plug boot (2) snugly onto 
spark plug terminal (1) of the proper 
size. (Note: If terminal has 
detachable SAE adapter nut, it must 
be attached.) 
A loose connection between spark 
plug boot and ignition wire 
connector in the boot may create 
arcing that could ignite combustible 
fumes and cause a fire.If the engine is down on power, check 
the...

24 English / USA
BR 340, BR 340 L, BR 420, BR 420 C Replacing the starter rope
:Remove the screws (1).
:Take the starter cover (2) off the 
engine.:Remove the spring clip (3). 
:Remove the rope rotor with washer 
(4) and pawl (5).:Ease the cap (6) out of the starter 
grip. 
:Remove remaining rope from the 
rotor and grip.
:Tie a simple overhand knot in the 
end of the new starter rope (see 
Specifications) and then thread the 
rope through the top of the grip and 
the rope bushing (7).
:Refit the cap in...

25 BR 340, BR 340 L, BR 420, BR 420 CEnglish / USA
:Thread the rope through the rotor 
and secure it in the rotor with a 
simple overhand knot.:Fit the pawl (5) in the rotor and slip 
the washer (4) over the starter post.
:Use a screwdriver or suitable pliers 
to install the spring clip (3) on starter 
post and over the peg on the pawl  – 
the spring clip must point clockwise 
– see illustration. 
Go to “Tensioning rewind spring”.Replacing a broken rewind spring
:Lubricate the new spring with a few...

26 English / USA
BR 340, BR 340 L, BR 420, BR 420 C :Fit new spring housing – bottom 
plate must face downward. Engage 
outer spring loop over the lug.
:Refit the rope rotor.
Go to “Tensioning rewind spring”.
If the spring pops out and uncoils 
during installation: Refit it in the 
spring housing in the counter-
clockwise direction – start outside 
and work inward.Tensioning rewind spring
:Make a loop in the unwound starter 
rope and use it to turn the rope rotor 
six full revolutions in the direction of...

27 BR 340, BR 340 L, BR 420, BR 420 CEnglish / USA
For periods of about 3 months or longer:
:Drain and clean the fuel tank in a 
well ventilated area.
:Dispose of remaining fuel and 
cleaning solution properly in 
accordance with local 
environmental requirements.
:Run engine until carburetor is dry – 
this helps prevent carburetor 
diaphragms sticking together.
:Thoroughly clean the machine – pay 
special attention to the cylinder fins 
and air filter.
:Store the machine in a dry, high or 
locked...

28 English / USA
BR 340, BR 340 L, BR 420, BR 420 C 1) STIHL recommends that this work 
be done by a STIHL servicing dealerMaintenance ChartThe following maintenance intervals apply to normal operating conditions only.
If your daily working time is longer than normal or operating conditions are 
difficult (very dusty work area etc.), shorten the specified intervals accordingly.
before 
starting work
after finishing
work or daily
after each
refueling stop
weekly
monthly
every 12 months
if problem
if...

29 BR 340, BR 340 L, BR 420, BR 420 CEnglish / USA
    1 Nozzle, straight* 
  2 Nozzle, curved* 
  3 Blower tube* 
  4 Blower tube 
  5 Control handle 
  6 Throttle trigger 
  7 Setting lever 
  8 Stop switch 
  9 Pleated hose 
10 Harness 
11 Back plate 
12 Back padding
13 Air filter
14 Antivibration elements
15 Spark plug boot
16 Muffler (with spark arresting 
screen)*
17 Carburetor adjusting screws
18 Choke knob
19 Starter grip
20 Fuel filler cap
21  Fuel tank
# Serial number
* see “Guide to Using this...