Yamaha WaveRunner VXR VX1800A, Service Manual

Page: 92 / 318

5-1
Engine unit (check and adjustment)
Engine unit (check and
adjustment)
Compression pressure check
Make sure that the battery voltage is more than
12 V.
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.
1. Place the watercraft in a horizontal posi-
tion.
2. Start the engine and warm it up for 5 min-
utes or more at engine idle speed.
3. Stop the engine.
4. Remove the ignition coils and spark plugs.
5. Disconnect the fuel injector couplers.
TIP:
Be careful not to get water or any other foreign
substances in the spark plug holes.
6. Install the special service tools “1” and “2”.
7. Crank the engine until the reading on the
compression gauge stabilizes.
8. Measure the compression pressure for all
cylinders according to steps 6 and 7.
TIP:
Measuring conditions: Ambient temperature
20 °C (68 °F), with spark plugs removed from
all cylinders. The figures are for reference only.
9. If the compression pressure is below spec-
ification, squirt a few drops of engine oil
into the cylinder and measure again.
10. Install the spark plugs, and then tighten
them to the specified torque.
11. Install the ignition coils.
12. Connect the fuel injector couplers.
Compression gauge “1”
90890-03160
Compression gauge “1”
YU-33223
Compression gauge extension “2”
90890-06563
1
2
Compression pressure
Minimum
780 kPa (7.8 kgf/cm², 113.1 psi)
Compression pressure (with engine oil add-
ed into the cylinder)
Reading Check
Higher than without
engine oil Piston ring and pis-
ton
Same as without en-
gine oil
Valve clearance,
valve, valve seat,
cylinder head, and
cylinder head gasket
Spark plug
25 Nm (2.5 kgf·m, 18.4 ft·lb)