Spark Plug Reach; Spark Plug Electrode Diagram; Sooty Plug View; Overheated Plug View - Honda C50 Shop Manual

78
figure
5- 24.
Spark plug reach
0 X
Standard reach Reach too long
Figure 5- 25. Spark plug electrode
figure 5- 26. Sooty plug
Figure 5-27. Overheated plug
5. ELECTRICAL SYSTEM
X
Reach too short
The correct spark plugs for the different models
ore shown in Fig. 5- 23.
3. SPARK PLUG REACH
The reach of the spa rk plug refers to length of
the th readed section. Different model mot o rcycles
hove cylind er head designed with different depth of
spark plug hole, th erefore, the spark plug with the
proper reach shou ld be used. (Fig. 5- 24, 5- 25)
The following unsatisfactory conditions will occu r
if plugs of improper reach ore used.
CD
Reach too long
a. Carbon wil l be deposited on the exposed thread
and cause damages to the threads in the spark
plug hole during p lu g removal
b . The plug tip w ill become overheated, causing
p re-ignition.
®
Reach too short
a. Carbon wi ll be deposited on the threads at the
bottom of the plug hole and when t he spark
plug of the proper reach is install ed, t he plug
hole threads will be damaged.
b. Du e to the cavity left by the short reach, ex-
haust gas will accumulate causing decrease in
power output, overheating, engine malfunction .
4. SPARK PLUG REACH
The spark plug firing, rega rd! ess of w hether th e
primary power supply is f rom on A.C. Generator or
a D.C. sou rce, is produced by the high vo ltage
seconde ry coil. The voltage generated will vary with
t he engine speed, however, with the . proper spark
gop, there is sufficient vo ltage to produce a spark
for t he required exp losion . If the spark gop is too
wide, a very high vo ltage is necessary to produce a
spa rk and, in w hich case, a misfire wil l result at low
speed.
On the other hand, if the gop is t oo narrow, a
spark w ill be produced at a very low vo ltage and
since the spark will be of a low energy, on in compl ete
explosio n wi ll toke p lace, resulting i n engine malfunc-
tion.