TROUBLESHOOTING
d.
Dirty or clogged
air
filter element.
e. Carburetor
in
co
rrec
tl
y adjusted (
100
lean or
too
r
ic
h).
f.
Choke valve stuck.
g.
Clogged jet(s)
in
the carburetor.
h. Carburetor n
Oat
height incorrect.
Engine Backfir
es-
Ex
pl
os
ions in Mumers
a. Fouled or improperly gapped spark plug.
b. Spark plug cap
fa
ult
y.
c. Ignition cable
in
s
ul
a
ti
on deteriorated (shorti
ng
o
ut
).
d. Ignition timing incorrect.
c. I
mproper
va
lve timing.
f.
Contam
in
ated fuel.
g.
Burned
or damaged intake andlor exhaust
va
lves.
h. Weak
or
broken inlakc andl
or
exhaust val
ve
springs.
Pre-ignition (Fuel
Mixture
Ign
it
es Berore Spa
rk
Plug Fires)
a. Hot S
pOi
in
combustion chamber (piece
of
ca
rbon
).
h.
Valve(s) stuck
in
guide.
c. Overheating engine.
Smoky Exhaust
and
Engine Runs Roughly
a.
Ca
rburetor mix.ture too rich.
b. Choke not operating correc
tl
y.
c. Water
or
other contaminants
in
fuel.
d. Clogged fuel line.
e. Clogged
air
filter clement.
Engine
loses
Power
at
Normal
Ridin
g
Speed
a.
Ca
rbur
etor inco
rre
c
tl
y adjusted.
b.
Engine ove rheating.
c. Improper igni
ti
on timing (faulty component
in
system).
d. Weak ignition signal generator.
e. Weak or faulty ignitor unit.
f.
In
correctly gapped spark plug.
g. Weak ignition
co
il.
h. Obstructed mufflers.
i. Dragging brake(s).
27
Engine
Lacks Acceleration
a. Carburetor mixture t
oo
l
ean.
b. Clogged fuel line.
c. Improper ignition timing (faulty
co
mponent
in
system).
d. Improper
va
lve clearance.
e. Dragg
in
g brake(s).
ENGINE NOISES
I.
Kn
ocking or pinging (luring acceleration-
Cau
se
d
by
using a lower
OC
tane
fu
el than recom·
me
nd
ed. M
ay
also
be
caused
by
poor
fu
el. Pinging
can also be caused by a spark plug
of
the wrong
heat range. Refer to
Spark
Plll
g Select
ion
in
Chapter Three.
2. Slapping or rauling noises at low speed or
during accelerOlion-May be
ca
u
sed
by
pi
ston slap
(excessi
ve
piston to cylinder wall clea rance).
3.
Kn
ock
in
g or
rap
ping while deceleratin
g-
Usually caused
by
excessive rod bearing clearance.
4.
Persistent knocking lind vib
rat
ion
-Us
ually
caused by excessive main bearing clearance.
5. Rapid on-of! squeal
-Com
pre
ss
ion leak around
cylinder head gasket or spark plugs.
EXCESSIVE VIBRATION
Thi
s
ca
n be
difficult
10
find
wi
thout
disassembling the engine. Usually th is
is
cau
se
d
by
loose engine mounting hardware or faulty
balancer assembl
y.
FRONT SUSPENSION
AND STEERING
P
oor
handling may be caused
by
improper
ti
re
pre
ss
ure. a damaged or bent frame
or
front stee
ri
ng
components. a worn front fork assembl
y.
worn
wheel bearings or dragging brakes.
BRAKE PROBLEMS
Sticking brake pads
or
shoes may
be
caused
by
a s
tu
ck
pi
ston
in
a ca
li
per ass
emb
ly
or
warped pad
shim
or
disc or out
-of
-round
drum
.
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