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NGK Spark BR8ES plugs
The proper spark plug for use in
most of the Rotax engines is the NGK B8ES, or other brand name
equivalent, (Champion spark plugs are not recommended, nor are
they factory authorized for ultralight
use.)
If using a spark plug with an BR
in its heading, (usually used for ignition noise suppression) such
as NGK BR8ES, a resistor cap should not be used. This is because
of the double resistance supplied when using both a resistor plug
and resistor cap. It is advisable with engines running in the
inverted position to use a spark plug with an extended electrode.
This aids in stopping spark plug fowling. Look for a BP in its
heading (NGK BP 8ES).
When removing or installing the
spark plug cap make sure that the cap is turned, in the rotation
necessary to tighten the screw on cap on top of the spark plug,
otherwise the improper removal of the cap results in the backing
off of the screw on cap and the possible loss of spark to the
engine, when the spark plug cap falls off.
Also see resistor plugs vs. resistor caps
The recommended gap on the spark
plugs is .015 to .019 of an inch. These plugs are capable of running for
over 20 hours trouble free on a points and condenser engine and up
to 50 hours trouble free on a dual CDI ignition engine (if proper
fuel and oil are used and the engine is in proper tune). They
should be checked on a regular basis however, and replaced at the
first sign of a miss or after severe flooding of the engine.
If using a cylinder head temp
gauge, removal of the ring on the bottom of the spark plug is
recommended, since the gauge sending unit replaces it. (Cylinder
head temperatures should range in the 300 to 400 degree F range.)
In practice, a properly tuned
engine should show a nice chocolate, or brown color on the spark
plug, white indicates an engine running hot, while black indicates
one running to rich. Any sign of aluminum on the spark plug
indicates a problem of a very serious nature, and requires your
immediate attention
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