Yamaha YZFR1W 2007, Service Manual

Page: 93 / 429

ENGINE
3-10
10. Install:
• Radiator upper bolts
• Radiator lower bolt
Refer to "RADIATOR" on page 6-1.
11. Install:
• Side cowlings
• Lower cowlings
Refer to "GENERAL CHASSIS" on page 4-
1.
EAS20710
MEASURING THE COMPRESSION PRES-
SURE
The following procedure applies to all of the
cylinders.
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. Disconnect:
• Ignition coils
4. Remove:
• Ignition coils
• Spark plugs
CAUTION:
ECA13340
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
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.
WARNING
EWA4C81007
To prevent sparking, ground all speak 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 gauge
90890-03081
Engine compression tester
YU-33223
Extension
90890-04136
Standard compression pres-
sure (at sea level)
1480 kPa/350 r/min (210.5 psi/
350 r/min) (14.8 kgf/cm²/350 r/
min)
Minimum–Maximum
1290–1660 kPa (183.5–236.1
psi) (12.9–16.6 kgf/cm²)