ENGINE FAULTS
A
number
of
possible
faults
are
listed
below,
together
with likely
causes.
A. Engine refuse to start
a) Plug not sparking, because
1. Plug
oiled
up,
da
mp,
shorted
or
damaged,
2. Exterior
of
plug
wet,
3.
Igniti
on
lead
loose
or
broken,
4.
Short-circuit
button
jams,
or
lead
s
from
engine
are
damaged,
5.
Breaker
contacts
oiled
up,
damp
or
burnt
,
6. I
gnition
armature
or
condense
r
damaged.
b)
No
fuel reaching engine, because
1.
No
fuel
in
tank,
2. Fuel cock
closed,
3. Fuel
strainer
clogg
ed,
4.
Fuel line
blocked,
5. J
ets
clogged.
c)
Fuel mixture not ignitable, because
1.
Carburettor
flooded,
2.
Water
in
carburettor
,
3.
Infiltrated
air
due
to
loose
carburettor
.
d)
Lack
of
compression, because
1.
Piston rings
broken,
2.
Piston
an
d cylinder
worn,
3. Ve
nt
coc
k
on
cran
kcase
op
en,
4.
Cylinder
he
ad
or
spark
plug
loo
se.
B.
Engine lacks
power
a)
Due
to
dir
ty components, because
1.
Intake
silencer
soiled,
2. Exhaust
and
transfer
ports
in
cylinder
clogged
with
carbon
.
3.
Th
ick c
arbon
depo
sit in cylind
er
head,
4.
Fuel
tank
gets
no
air
(fi
ller
cap),
5.
Spark
plug
vitrified.
b)
Due to lack
of
compression, because
(see
under
"Lack
of
compr
essio
n,
because
"
).
C.
Other
engine faults
a) Engine
runs
unevenly, because
1. Ig niti
on
l
ead
loose
or
damaged,
2.
Engine
overheats;
fuel
vapor
lock
in
carbur
e
tto
r
interrupts
fuel
supply
,
3.
Contact
breaker
points
oiled
up
or
fu
sed,
44
4. Locating pin
for
contact
breaker
arm
worn,
5.
Spar
k
plug
or
sp
ark
plug
terminal
or
ignition
armature
no
t
in
order.
b)
Engine four-strokes
and
does not
reach speed, because
1.
Chok
e
closed,
2.
Carbu
ret
tor
floods
due
to
clogged
or
damaged
inlet
needle
seati
ng,
3. Exhaust du
ct
clogged
with
carbon,
4.
Carburettor
setting
incorrect
or
j
ets
loose,
5.
In
take
silenc
er
soiled.
c)
Engine pinks
at
full speed under
load,
because
1. I
gnition
too
far
advan
c
ed,
2.
Combu
stion
chamber
needs
decarboniz
ing,
3. Cooling fins soile
d,
4. Small
end
bushing
worn
.
d) Engine backfires
or
spits into
carburettor, because
1.
Engine
not
getting
adequa
te
fuel,
2.
Spark
plug
glows
due
to
incor
r
ect
h
eat
va
lue,
3.
Spark
plug
shorted,
dirty
or
vitrified,
4. E
ngine
getting
infiltrat
ed
air,
5. W
ater
in
carbur
e
ttor
.
e)
Engine gets too
hot
and piston
seizes, because
1.
Engine
badly
decarbonized
(piston cr
own
polished
clean
},
2.
Engine
not
getting
sufficient fuel,
3. C
arburettor
adjusted
incorr
ect
ly
or
wrong
oil u
sed,
4.
Coo
ling
fi
ns
on
cylin
der
and
cyl
inder
head
soil
ed
,
5.
There
are
pre
-ignitions.
f) Engine has no idling speed, because
1. Idling
adj
us
tment
screw
or idle s
top
screw
incorrectly
adjus
ted,
2.
Control
cab
le
for
butt
erfly
valve
wron
g
ly
adju
st
ed,
3. I
gnition
arl}'lature
dama
ged.
g)
Fu
el consumption
of
engine
is
too
high, b
ec
ause
1.
Fu
el
tank
, fuel line
or
carburettor
l
eaking,
2. Jets
too
l
arge
.
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