Honda C50 - CHARGING SYSTEM

5.6 SPARK PLUG
77
5.6 SP
PUG
::: -;; perfor ms one o= ·-e -:::s- - ~portent
- -~ -- - - ·ne engine igni io s,_ e ":l . Th e high
o ·:::;;;e ::: r oduced by the mogne·o o· · e i gnitio n coil
·s re::e·· ed by the spark plug O"O causes the high
e sio n spark
to jump across fro m he cente r electrode
of he sp ark plug to the side e lect rode within the
engine co mbustion chamber. The spa rk ignites the
compressed fuel mixture in the co mbustion chamber
and
produces on explos ion which operates the engine.
Even under various adverse
condi tions, durability and
r eliabilit y is required. (Fig. 5-21)
1. SPARK PLUG
The operation of the engine can be determined
by the condition of the plug. The firing area of the
insulator colored white, gray or light gray indicates
good cond ition and is performing satisfactoril y.
2. HEAT RANGE OF THE SPARK PLUG
The firing area of the spark plug insula tor is
exposed to car bon and oil while the engine is o perat -
ing, and to prevent its build-up, plugs are designed
to burn off any deposits by the heat of combustion.
Spark plugs which are too cold wil l not burn off the
carbon and oil deposits and wi ll cause sh or ting of
the high tension voltage resulting in the engine to
mis - fire. In the opposite case, the power ou tput will
be drastically reduced.
In order to prevent the above troubles, the surface
of the insulator firing area must be maintained at
approximately 500-870°C 1932- 1600 ° Fl range. This
temperature is referred to as the se lf-cl eaning
temperature.
The temperature of the spark plug will vary to a
considerable degree with the type engine and de-
sign, riding condi tion, and fuel.
In order for the plugs to function properly under
the different conditions, it is necessary for the plugs
to properly dissipate temperature of the plug caused
by the heat of combustion.
The
rate of hea t dissipation of the spark plug is
the
heat range of the spark plug . A spark plug which
readily dissipates the heat and which is difficult to
overheat is referred to as a "Cold Type", A spark
plug
which retains the heat and which will burn readily
is referred to as a "Hot T ype". On engine oper -
at ing at high temperature, a spark plug which is difficult
to overheat, in other words, the cold type spark plug
is used
and for engine operating at low temperature
a hot type spark plug is used. (Fig. 5- 22, 5- 23)
Figure
5-21. Spork plug
Meta l pack i ng
gap
Side electrode
Figure 5- 22 . Construction of spa rk plug
Hot typ e c -4 C I
c - 6
c - -s st? a o JJse
,.,
c - g - ~ -- -- - ~
c - ~-=~---·~ - ~
c - 1;- -- - --- g -- ~
c - ~ - __ ____ ::- ___ } ~
I C - , _ ----- .. ---- .iij
Cold tpe cr:
Hot type
( low te~era ra se
Cold type
( high temperature use )
Figure 5-23 . Hea range of spark pl ug