Generic Race 50 - Page 27

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Remove spark plug, observe
color of spark plug insulator
skirt and determine mixture
ratio of combustible mixture
according to various abnormal
situations.
Spark plug insulator skirt
renders black; in addition,
exhaust muffler gives off black
fume or blasts, accelerating
ability is poor or idle speed is
instable and engine is liable to
shutdown when it is running
under medium low speed
(comparatively normal when it is
running under high speed).
Spark plug insulator skirt
renders chocolate-
b
rown
S
p
ark plug insulator skirt
renders white; in addition,
intermittent engine stop,
carburetor backfire, or power
lack of engine, etc. occurs
during acceleration.
Combustible
mixture too rich
1. Check air cleaner for clogging
2. Check carburetor starting device
(i.e. starting richer system) for
proper operation
3. Check carburetor float for
insufficient height
Mixture ratio of
combustible mixture
normal
Check exhaust port of
cylinder block and
exhaust muffler for
clogging caused by
excessive carbon
de
p
osit
Check
lubrication
s
y
ste
m
Combustible
mixture too thin
Lubrication system
on 2/4 stroke engine
1. Check fuel cock for
proper operation
2. Check carburetor
float for height excess
3. Check all orifices
and tunnels on
carburetor for clogging
1. Check if volume of engine oil
in crankcase is sufficient
2. Check if viscosity of engine
oil in crankcase is too low or
engine oil is too dirty
3. Check oil filter for clogging
4. Check oil pump for proper
operation
5. Check lubricant ducts for
clogging