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

Catalytic Converter*

Power tools with a catalytic converter*
may only be operated with unleaded
gasoline and STIHL two-stroke
engine oils in a mix ratio of 50:1
(see chapter "Fuel").
The catalytic 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-
stroke engine oil are essential to
minimize harmful exhaust emissions
and ensure a long catalyst service life.
* see "Guide to Using this Manual"
BR 420

Checking the Spark Plug

If engine is down on power, difficult to
start or runs poorly at idle speed, first
check the spark plug.
: Remove the spark plug –
see "Starting / Stopping the Engine".
: Clean dirty spark plug.
: Check electrode gap (A) and
readjust if necessary – see
"Specifications".
: Rectify the problems which have
caused fouling of spark plug:
– To much oil in fuel mix.
– Dirty air filter.
– Unfavorable running conditions.
: Fit a new spark plug after
about 100 operating hours – or
sooner if the electrodes are badly
eroded.
Install only suppressed spark plugs
of the type approved by STIHL –
see "Specifications".
To reduce the risk of arcing
and fire:
: If the spark plug comes with a
detachable adapter nut (1), screw it
on firmly.
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