Yamaha WaveRunner VX 700, Service Manual

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3-5
MNT
Maintenance
4. Measure the spark plug gap
b
. Replace
if out of specification.
5. Tighten the spark plugs to the specified
torque.
TIP:
Before installing a spark plug, clean the gas-
ket surface and spark plug surface.
6. Install the spark plug caps.
Compression pressure measurement
When starting the engine to measure the
compression pressure on land, make sure
to connect a garden hose to the watercraft
for proper water supply.
TIP:
Make sure that the battery voltage is more
than 12 V.
1. Place the watercraft in a horizontal posi-
tion.
2. Start the engine and warm it up for 6 min-
utes or more at engine idle speed.
TIP:
Warm up the engine an additional 5 minutes
if the ambient temperature is 20 °C (68 °F) or
less.
3. Stop the engine.
4. Remove the spark plug caps, and then
remove the plugs.
5. Install the special service tool
1
.
6. Fully open the throttle lever.
7. Crank the engine until the reading on the
compression gauge stabilizes.
8. Measure the compression pressure for
all cylinders according to steps 5–7.
9. If the compression pressure is below
specification, squirt a few drops of engine
oil into the cylinder and measure again.
10. Install the spark plugs, and then install
the spark plug caps. See “Spark plug
check” (3-4).
Specified spark plug (manufacturer):
BR8HS (NGK)
Spark plug gap
b
:
0.6–0.7 mm (0.024–0.028 in)
Spark plug: 25 N·m (2.5 kgf·m, 18.4 ft·lb)
b
Compression gauge
1
: 90890-03160
Compression pressure (reference data):
590 kPa (5.9 kgf/cm
2
, 84 psi)
Compression pressure
(with engine oil added into the cylinder)
Reading Check
Higher than without
engine oil Piston ring and
piston
Same as without
engine oil Cylinder head
gasket or piston
1