IAME Parilla Norswift 60cc - Spark-Plug Thermal Degree

18 MAN-071
12- SPARK-PLUG THERMAL DEGREE
The engine is supplied with a standard NGK BR9EG spark plug which represents a good
compromise between the needs of a good break-in and the racing needs in normal
conditions.
The colour of the various parts of the spark plug more exposed to the combustion flames
gives a good indication on the adequacy of the thermal degree and on the carburetion. It is
necessary though to understand which of the two parameters has to be changed and only
the experience tells how to identify the most proper thermal degree of a spark plug as lean
or rich mixtures can generate the same final look which can be also achieved with a hot or
cold spark plug.
See table:
an excessively warm spark plug shows the
symptoms listed aside.
ATTENTION:
Use a warmer spark plug with cold or rainy
climates
 Extremely clear color, porous look and
calcification of the electrodes and of the internal
insulator.
 Irregularities in the ignition, preignition and
detonation with tendency to perforate the top of the
piston .
 Note: some of these symptoms can be
achieved also with lean mixtures.
A correct thermal degree shows:
 Color of the insulator end from yellow grey to
dark brown for mixtures respectively lean or rich.
An excessively cold spark plug shows the
symptoms, listed aside.
ATTENTION:
Use a colder spark plug with hot climates.
 Insultator end and electrodes covered with black
shady soot.
 Ignition difficulties.
 Note: a wet or oily electrode could also mean
an excessively rich mixture.
COMPARISON TABLE BASED ON
THE THERMAL DEGREE
HOT
COLD
NGK
BR8EG
BR9EG