TOHATSU NB-1000 Service Manual page 89

SECTION 4
CYLINDER COMPRESSI0N TEST
1. Operate engine 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 spark plug(s) 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
2.5 / 3.5
5
8 / 9.8
9.9 / 15
18
25 / 30
40
* Compression variation among cylinders should not exceed 15 psi
[103 kPa / 1.05 kg/cm
If variation of cylinder compression, on two cylinder engines,
exceeds 15 psi [103 kPa / 1.05 kg/cm
• Scored cylinder walls.
• Piston damage.
• Head gasket damage.
• Stuck or broken piston rings.
On two cylinder models, if cylinder compression is equal, engine is
difficult to start and runs poorly, check for the following:
• Scored cylinderwalls.
• Piston damage.
• Stuck or worn piston rings.
4-8
WARNING
Cylinder Compression*
psi [kPa / kg / cm
78.0 [539.0 / 5.5]
78.0 [539.0 / 5.5]
56.9 [392.0 / 4.0]
113.7 [784.0 / 8.0]
106.6 [735.0 / 7.5]
99.6 [686.0 / 7.0]
106.6 [735.0 / 7.5]
] on two cylinder engines.
2
], check for the following:
2
]
2
T1162
1-/ 2-Cylinder