Yamaha YJ50RN Service Manual page 55

MEASURING THE COMPRESSION PRESSURE
1
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
6. Measure:
• compression pressure
Out of specification → Refer to steps (c)
and (d).
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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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.
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CHK
ADJ
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