Yamaha XVS1100(L) Service Manual page 71

MEASURING THE COMPRESSION PRESSURE
CAUTION:
Before removing the spark plugs, use com-
pressed air to blow away any dirt accumu-
lated in the spark plug wells to prevent it
from falling into the cylinders.
5. Install:
S compression gauge 1
Compression gauge set:
90890-03081
6. Measure:
S compression pressure
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 cylinder and
measure again.
S Refer to the following table.
Compression pressure
(with oil applied in the cylinder)
Reading Diagnosis
Higher than Piston wear or damage
! Repair.
without oil
Piston ring(-s), valves, cylin-
Same as
der head gasket or piston
without oil
possibly defective ! Repair.
Compression pressure (at sea
level)
Standard:
1,000 kPa (10 kg/cm
Minimum:
900 kPa (9 kg/cm
Maximum:
1,100 kPa (11 kg/cm
a. Turn the main switch to "ON".
b. With the throttle wide open, crank the engine
until the reading on the compression gauge
stabilized.
WARNING
To prevent sparking, ground all spark plug
leads before cranking the engine.
NOTE:
The difference in compression pressure be-
tween cylinders should not exceed 100 kPa (1
2
kg/cm , 1 bar).
3-15
INSP
ADJ
2
, 10 bar)
2
, 9 bar)
2
, 11 bar)