Catalytic Converter; Checking The Spark Plug - Stihl BR 420 Instruction Manual

Fine tuning for operation at high
altitude
A slight correction of the setting may be
necessary if the engine does not run
satisfactorily:
N
Check the standard setting.
N Warm up the engine.
N
Turn high speed screw (H)
clockwise (leaner) – no further than
stop.
If the setting is too lean there is a
risk of engine damage due to
insufficient lubrication and
overheating.
BR 420

Catalytic Converter

Power tools with a catalytic converter
(depending on model) must be run on a
50 : 1 mixture of unleaded gasoline
and STIHL two-stroke engine oil or
equivalent two-stroke engine oil – see
chapter on "Fuel".
The catayltic converter integrated in the
muffler reduces the harmful emissions in
the exhaust gas.
The correct carburetor setting (if
adjustable) and strict observance of the
prescribed mix ratio of gasoline and two-
stroke engine oil are essential to
minimize harmful emissions and ensure
a long catalytic converter service life.

Checking the Spark Plug

If the engine is down on power, difficult
to start or runs poorly at idle speed, first
check the spark plug.
N Remove the spark plug – see
"Starting / Stopping the Engine".
N Clean dirty spark plug.
N Check electrode gap (A) and
readjust if necessary – see
"Specifications".
N Rectify the problems which have
caused fouling of the spark plug.
Possible causes are:
– Too much oil in fuel mix.
– Dirty air filter.
– Unfavorable running conditions.
English
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