Yamaha WaveRunner FX140 Manuel D'entretien page 230

POWR
ENGINE UNIT
7. Measure:
• Compression pressure
Out of specification → Refer to steps (b)
and (c).
Minimum compression pressure
(reference data):
1,080 kPa
(10.8 kgf/cm
Measurement steps:
a. With the throttle wide open, crank the
engine until the reading on the compres-
sion gauge stabilizes.
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
2
kPa (1 kgf/cm
b. If the compression pressure is extremely
high, check the cylinder head, valve sur-
faces and piston crown for carbon depos-
its.
Carbon deposits → Eliminate.
c. If the compression pressure is below the
minimum specification, squirt a few drops
of oil into the cylinder and measure
again.
Refer to the following table.
Compression pressure
(with oil applied into the cylinder)
Reading
Higher than
without oil
Same as without
oil
8. Install:
• Spark plug
Spark plug:
13 N • m (1.3 kgf • m, 9.4 ft • lb)
5-5
2
, 157 psi)
, 14 psi).
Diagnosis
Piston wear or
damage → Repair.
Piston ring(s),
valves, cylinder
head gasket or pis-
ton possibly defec-
tive → Repair.
E