Yamaha YZFR6X(C) 2008 Service Manual page 105

NOTE:
Insufficient compression pressure will result in
a loss of performance.
1. Measure:
• Valve clearance
Out of specification → Adjust.
Refer to "ADJUSTING THE VALVE
CLEARANCE" on page 3-4.
2. Start the engine, warm it up for several
minutes, and then turn it off.
3. Remove:
• Side cowling assembly
Refer to "GENERAL CHASSIS" on page
4-1.
• Radiator
Refer to "RADIATOR" on page 6-1.
4. Remove:
• Ignition coils
• 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.
5. Install:
• Compression gauge "1"
• Extension "2"
Compression gauge
90890-03081
Engine compression tester
YU-33223
Extension
90890-04136
6. Measure:
• Compression pressure
Out of specification → Refer to steps (c)
and (d).
▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼
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.
EWA12940
WARNING
To prevent sparking, ground all spark plug
leads before cranking the engine.
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
2
Same as without oil
1
▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲
7. Install:
• Spark plugs
• Ignition coils
3-10
Standard compression
sure (at sea level)
1600 kPa/400 r/min (227.6 psi/
400 r/min) (16.0 kgf/cm²/400 r/
min)
Minimum–maximum
1350–1650 kPa (195.8–239.3
psi) (13.5–16.5 kgf/cm²)
Diagnosis
Piston ring(s) wear or
damage → Repair.
Pistons, valves, cylin-
der head gasket or
piston ring(s) possi-
bly defective →
Repair.
Spark plug
13 Nm (1.3 m·kg, 9.6 ft·lb)
ENGINE
pres-