Yamaha F6AMH, Service Manual

Page: 124 / 510

POWER UNIT
MEASURING THE COMPRESSION
PRESSURE
NOTE:
Before measuring the compression
pressure, warm-up the engine. Correct
measurement cannot be obtained when the
engine is cold.
Measure:
Compression pressure
Below minimum compression
pressure
Check the valve
clearance, valve face, valve seat,
piston rings, cylinder sleeve, piston,
cylinder head gasket and cylinder
head.
Measuring steps:
(1)Checking the valve clearance.
Refer to “ADJUSTING THE VALVE
CLEARANCE” on page 3-15.
(2)Remove the spark plugs 1 .
CAUTION:
Before removing the spark plugs, use
compressed air to blow away dirt
accumulated in the spark plug well to
prevent it from falling into the cylinder
that is being tested.
(3)Install the compression gauge
2
into
the spark plug hole to be measured.
(4)Open the throttle valve wide.
(5)Crank the engine using the recoil
starter (manual starter model) or
starter motor (electric starter model)
until the reading on the compression
gauge stabilizes.
(6)Remove the compressin gauge 2 .
(7)Install the spark plugs 1 .
Compression pressure (Reference
value):
950 kPa (9.5 kgf/cm
2
, 135.1 psi)
Compression gauge:
YU-33223/90890-03160
Spark plug:
25 N m (2.5 kgf m, 18.4 ft lb)
3-17