Honda CB160 Shop Manual page 94

90
5. ELECTRICAL PARTS
(bl Heat reduction
The plug is heated by combustion due to rotation
of the engine being transmitted as shown by arrow
in Fig. 5. 35. By regulating the heat dissipated
and heat transmitted from the combustion gas, the
ignition section maintains a certain constant tem-
perdture. (Refer to Fig. 3. 35)
4. Necessity of spark plugs with different
heat values
Fig.
5. 35
Temperature dissipation (Quantitative difference of heat received by plugs)
FOR LOW HEAT FOR MEDIUM HEAT FOR HIGH HEAT
HOT TYPE MEDIUM TYPE COLD TYPE
Fig.
5. 36
Sectional view of plug characteristics
IGNITION TOO EARLY
SMOOTH RUNNING
f' . "···t·······.i····:,1
LOW POWER
HOT TYPE SPARK PLUG
HIGH POWER
IGNITION TOO EARLY
SMOOTH RUNNING
sra
COLD TYPE SPARK PLUG
fig.
5. 37
Plug comparison (by operation status)
Spark plug
tNGKJ
Standard value Spark gap
0.7
mm
(.027
11
1
Maintenance value
Spark gap Below
0.5
mm
(.019
11
1
,,
Above
0.9
mm
(.035
11
)
When rising is
D-6H
is employed
intense
With rising
D-9H
is employed
tendencv
Fig.
5. 38
The quantity of heat the plug receives from the
engine differs extensively due to 'engine type (air
cooled, water-cooled, 2-cycle, or 4-cycle engine),
design (compression ratio, combustion chamber profile,
or position of plug installation), and operational status
(speed, load, difference of fuel, rough or smooth road
conditions). Hence, for efficient performance under
such varied conditions, several types of plugs with
different heat dissipation ratios are required. The
ratio of dissipation is termed " Plug heat value "
The .heat value is determined by construction, profile,
and dimentions. The plug with a superior dissipation
ratio is termed " cold type " (for high temperatures);
conversely, the one well heated without dissipating
is termed "Hot type" (for low temperatures).
(Refer
to Fig.
5. 36)
In Model CB 125/CB 160, a standard NGK
D--8 H, 12 mm plug is employed. However, selection
of plugs with suitable heat values must be in accord-
ance with climatic conditions.
(Refer
to Fig.
5.
37)
When the plug gap is incorrect, adjustm~nt should
be performed by striking the side electrode. When
adjustment cannot be obtained due to electrode wear,
the plug should be replaced.
(Refer to Fig. 5. 38)