Engine Unit (Check And Adjustment); Compression Pressure Check - Yamaha Waverunner VXS VX1800 Service Manual

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".
1
Compression gauge "1"
90890-03160
Compression gauge "1"
YU-33223
Compression gauge extension "2"
90890-06563
7. Crank the engine until the reading on the
compression gauge stabilizes.
2

Engine unit (check and adjustment)

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.
Compression pressure
Minimum
780 kPa (7.8 kgf/cm², 113.1 psi)
9. If the compression pressure is below spec-
ification, squirt a few drops of engine oil
into the cylinder and measure again.
Compression pressure (with engine oil add-
ed into the cylinder)
Reading
Higher than without
engine oil
Same as without en-
gine oil
10. Install the spark plugs, and then tighten
them to the specified torque.
Spark plug
25 Nm (2.5 kgf·m, 18.4 ft·lb)
11. Install the ignition coils.
12. Connect the fuel injector couplers.
5-1
Check
Piston ring and pis-
ton
Valve clearance,
valve, valve seat,
cylinder head, and
cylinder head gasket