Yamaha 5KM2-AE1 Service Manual page 100

MEASURING THE COMPRESSION PRESSURE
6.Measure:
Compression pressure
G
Above the maximum pressure:
Inspect the cylinder head, valve surfaces,
and piston crown for carbon deposits.
Below the minimum pressure:
Squirt a few drops of oil into the affected cyl-
inder and measure again.
Refer to the table below.
Compression pressure
(with oil introduced into cylinder)
Reading
Higher than
without oil
Same as
without oil
Compression pressure (at sea level):
Standard:
1,324 kPa
(13.24 kg/cm
Minimum:
1,150 kPa
(11.5 kg/cm
Maximum:
1,480 kPa
(14.8 kg/cm
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Measurement steps:
G
Crank over the engine with the electric
starter (be sure the battery is fully charged)
with the throttle wide-open until the compres-
sion reading on the gauge stabilizes.
WARNING
When cranking the engine, ground the
spark plug lead to prevent sparking.
*****************************************************
7.Install:
Spark plug
G
3 - 25
CHK
ADJ
Diagnosis
Worn or damaged pistons
Defective ring(s), valves,
cylinder head gasket or
piston is possible.
2
, 188.31 psi)
2
, 163.57 psi)
2
, 210.50 psi)
18 Nm (1.8 m • kg, 13 ft • lb)