Cylinder Compression Test - TOHATSU 40 Service Manual

CYLINDER COMPRESSION TEST

1. Operate engine up to normal operating temperature.
2. Stop engine.
3. Disconnect the magneto leads to disable the ignition system.
Ignition system must be disabled to prevent
accidental engine startup during compression
test.
4. Remove all spark plugs and install thread-type compression
1
tester in spark plug hole.
5. Place throttle in fully open position and crank engine with starter
through at least four compression strokes. Take reading for each
cylinder and verify specified pressure is obtained:
Model
40 / 50
60 / 70
80 / 90
115 / 120 / 140
* Compression variation among cylinders should not exceed 15
psi [103 kPa / 1.05 kg/cm
If variation of cylinder compression exceeds 15 psi [103 kPa / 1.05
kg/cm ], check for the following:
2
• Scored cylinder walls.
• Piston damage.
• Head gasket damage.
• Stuck or broken piston rings.
If cylinder compression is low, engine is difficult to start and runs
poorly, check for the following:
• Scored cylinder walls.
• Piston damage.
• Stuck or worn piston rings.
3-/ 4-Cylinder
WARNING
Cylinder Compression*
psi [kPa / kg/cm
117 [800 / 8.2] ± 13 %
121 [830 / 8.5] ± 13 %
117 [810 / 8.2] ± 13 %
128 [880 / 9.0] ± 13 %
].
2
]
2
POWERHEAD
T1162
4-9