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.