Compression Pressure Measurement - Yamaha VMX12H Supplementary Service Manual

COMPRESSION PRESSURE MEASUREMENT

2-17
COMPRESSION PRESSURE MEASUREMENT
NOTE:
Insufficient compression pressure will result in
performance loss.
1. Measure:
clearance
Out of specification
2.
Warm up the engine.
3.
Remove:
plugs
4.
Measure:
pression pressure
By the following measurement steps.
Compression pressure measurement steps:
the Compression
33223)
using an adapter.
over the engine with the electric
starter (be sure the battery is fully charged)
with the throttle wide open until the com-
pression reading on the gauge stabilizes.
with specified levels (See
chart)
Compression Pressure (at sea level):
Standard:
980 (10
Minimum:
882 (9
Maximum:
(12
When cranking the engine, ground all of the
spark plug leads to prevent sparking.
the previous steps for the other
cylinders.
pressure falls bellow the minimum level:
Squirt a few drops of oil into the affected
1
)
.
cy I inder
2)
Measure the compression again.
Compression Pressure
(with oil introduced into
Adjust.
142 psi)
128 psi)
171
Diagnosis
pistons