Yamaha FZS6W Service Manual page 96

• Battery
Refer to "GENERAL CHASSIS" on page 4-
1 and "CHECKING AND CHARGING THE
BATTERY" on page 8-68.
• Battery box
• Battery box bracket
Refer to "GENERAL CHASSIS" on page 4-
1.
• Heat protector plate
• Cover
• Ignition coils
4. Disconnect:
• Spark plug caps
5. Remove:
• Spark plugs
ECA13340
CAUTION:
Before removing the spark plugs, use com-
pressed air to blow away any dirt accumu-
lated in the spark plug wells to prevent it
from falling into the cylinders.
6. Install:
• Compression gauge "1"
Compression gauge
90890-03081
Engine compression tester
YU-33223
7. Measure:
• Compression pressure
Out of specification → Refer to steps (c)
and (d).
Standard
sure (at sea level)
1550 kPa/400 r/min (220.5 psi/
400 r/min) (15.5 kgf/cm²/400 r/
min)
Minimum–maximum
1300–1650 kPa (184.9–234.7
psi) (13.0–16.5 kgf/cm²)
compression pres-
▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼
a. Set the main switch to "ON".
b. With the throttle wide open, crank the
engine until the reading on the compres-
sion gauge stabilizes.
EWA4S81003
WARNING
To prevent sparking, ground all spark plug
leads before cranking the engine.
ECA13340
CAUTION:
Before removing the spark plugs, use com-
pressed air to blow away any dirt accumu-
lated in the spark plug wells to prevent it
from falling into the cylinders.
NOTE:
The difference in compression pressure
between cylinders should not exceed 100 kPa
(1 kg/cm², 14 psi).
c. If the compression pressure is above the
maximum specification, check the cylinder
head, valve surfaces and piston crown for
carbon deposits.
Carbon deposits → Eliminate.
d. If the compression pressure is below the
minimum specification, pour a teaspoonful
of engine oil into the spark plug bore and
measure again.
Refer to the following table.
Compression pressure (with oil applied into
the cylinder)
Reading
Higher than without
oil
Same as without oil
▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲
8. Install:
• Spark plugs
Spark plug
18 Nm (1.8 m·kg, 13 ft·lb)
9. Connect:
• Spark plug caps
10. Install:
• Ignition coils
• Cover
3-11
ENGINE
Diagnosis
Piston ring(s) wear or
damage → Repair.
Piston, valves, cylin-
der head gasket or
piston possibly defec-
tive → Repair.