Yamaha VINO YJ50RAP, Service Manual

Page: 59 / 228

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CHK
ADJ
MEASURING THE COMPRESSION PRESSURE
CAUTION:
@
Before removing the spark plug, use com-
pressed air to blow away any dirt accumu-
lated in the spark plug well to prevent it
from falling into the cylinder.
5. Install:
• compression gauge
1
Compression gauge
YU-33223
1
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 compression
gauge stabilizes.
WARNING
@
To prevent sparking, ground the spark plug
lead before cranking the engine.
c. If the compression pressure is above the
maximum specification, check the cylinder
head and piston crown for carbon deposits.
Carbon deposits
→
Eliminate.
Compression pressure
(at sea level)
Minimum
600 kPa (6.0 kg/cm, 85.3 psi)
Standard
800 kPa (8.0 kg/cm, 113.8 psi)
Maximum
1,000 kPa (10.0 kg/cm, 142.2 psi)
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