Yamaha RS90GTZ Service Manual page 44

COMPRESSION PRESSURE MEASUREMENT
Compression pressure
(with oil applied into cylinder)
Reading
Higher than
without oil
Same as
without oil
Standard compression pressure
(at sea level):
Standard:
1,650 kPa (16.5 kgf/cm
239.3 psi) at 400 r/min
Minimum:
1,440 kPa (14.4 kgf/cm
208.9 psi) at 400 r/min
Maximum:
1,850 kPa (18.5 kgf/cm
268.3 psi) at 400 r/min
Measurement steps:
• Set the engine stop switch to "RUN" and turn
the main switch to "START".
• With the throttle wide open, crank the engine
until the reading on the compression gauge
stabilizes.
WARNING
To prevent sparking, disconnect all ignition
coil couplers before cranking the engine.
TIP
The difference
between cylinders should not exceed 100 kPa
2
(1.0 kgf/cm , 14.5 psi).
7. Install:
• Spark plug
Spark plug:
13 Nm (1.3 m•kgf, 9.4 ft•lbf)
2-21
INSP
ADJ
Diagnosis
Piston ring(-s) wear or
damage → Repair.
Piston, valves, cylinder
head gasket or piston
possibly defective →
Repair.
Compression pressure
(at sea level)
2
,
2
,
2
,
in compression pressure