Engine Noises; Engine Lacks Acceleration; Engine Backfires; Engine Misfires During Acceleration - Yamaha V star 1100 Owner's Manual

TROUBLESHOOTING
2. Carburetor adjustment incorrect; mixture too
rich.
3. Choke not operating correctly.
4. Contaminants in the fuel.
5. Clogged fuel line.
6. Spark plugs fouled.
7. Ignition coil defective.
8. Ignitor unit or pickup coil defective
9. Loose or defective ignition circuit wire.
10. Short circuit from damaged wire insulation.
11. Loose battery cable connection(s).
12. Valve timing incorrect.

Engine Lacks Acceleration

1. Carburetor mixture too lean.
2. Clogged fuel line.
3. Improper ignition timing.
4. Dragging brake(s).
5. Slipping clutch.

Engine Backfires

1. Improper ignition timing.
2. Carburetor(s) improperly adjusted.
3. Lean fuel mixture.

Engine Misfires During Acceleration

1. Improper ignition timing.
2. Lean fuel mixture.
3. Excessively worn or defective spark plug(s).
4. Ignition system malfunction.
5. Incorrect carburetor adjustment.

ENGINE NOISES

Often the first evidence of an internal engine
problem is a strange noise. A new knocking, click-
ing or tapping sound may be an early sign of trou-
ble. While engine noises can indicate problems,
they are difficult to interpret correctly. They can se-
riously mislead inexperienced mechanics.
Professional mechanics often use a special
stethoscope to isolate engine noises. A home me-
chanic can do nearly as well with a length of dowel
or a section of small hose. Place one end in contact
with the area in question and the other end to the
front of your ear (not directly on your ear) to hear
the sounds emanating from that area. At first, this
will be a cacophony of strange noise. Distinguish-
ing a normal noise from an abnormal one can be dif-
ficult. If possible, have an experienced mechanic
help you sort out the noises.
Consider the following when troubleshooting en-
gine noises:
1. A knocking or pinging during acceleration is
usually caused by the use of a low octane fuel. It
may also be caused by poor fuel, a spark plug of the
wrong heat range or carbon buildup in the combus-
tion chamber. Refer to Spark Plugs and Compres
sion Test in Chapter Three.
2. Slapping or rattling noises at low speed or dur-
ing acceleration may be caused by excessive pis-
ton-to-cylinder wall clearance (piston slap).
NOTE
Piston slap is easier to detect when
the engine is cold and before the pis
tons have expanded. Once the engine
has warmed up, piston expansion re
duces piston to cylinder clearance.
3. A knocking or rapping while decelerating is
usually caused by excessive connecting rod bearing
clearance.
4. A persistent knocking and vibration that occurs
every crankshaft rotation is usually caused by worn
connecting rod or main bearing(s). Can also be
caused by broken piston rings or damaged piston
pins.
5. A rapid on-off squeal may indicate a compres-
sion leak around cylinder head gasket or spark
plug(s).
6. If valve train noise is evident, check for the fol-
lowing:
a. Excessive valve clearance.
b. Excessively worn or damaged camshaft.
c. Damaged cam chain tensioner.
e. Worn or damaged valve lifters and/or shims.
f. Damaged valve bore(s) in the cylinder head.
g. Valve sticking in guide.
h. Broken valve spring.
i. Low oil pressure.
j. Clogged cylinder oil hole or oil passage.
k. Excessively worn or damaged timing chain.
l. Damaged timing chain sprockets.
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