Service manual

CHK
ADJ
3-16
MEASURING THE COMPRESSION PRESSURE
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a. Set the main switch to “ON”.
b. With the throttle wide open and push the
“START” switch, then crank the engine until
the reading on the compression gauge sta-
bilizes.
w
To prevent sparking, ground the spark plug
lead before cranking the engine.
c. If the compression pressure is above the
maximum specification, check the cylinder
head, valve surfaces, and piston crown for
carbon deposits.
Carbon deposits
→
Eliminate.
d. If the compression pressure is below the
minimum specification, pour a teaspoonful
of engine oil into the spark plug bore and
measure again.
Refer to the following table.
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Compression pressure
(with oil applied into the cylinder)
Reading Diagnosis
Piston ring(s) wear
Higher than with-
or damage
→→
out oil
Repair.
Piston, valves, cyl-
Same as without inder head gasket
oil or piston possibly
defective
→→
Repair.
1
6. Install:
9
compression gauge
1
7. Measure:
9
compression pressure
Out of specification
→
Refer to steps (c)
and (d).
Compression gauge
90890-03081
Compression pressure
(at sea level)
Minimum
490 kPa (4.9 kg/cm
2
, 70 psi)/at 500 r/min
Standard
560 kPa (5.6 kg/cm
2
, 80 psi)/at 500 r/min
Maximum
630 kPa (6.3 kg/cm
2
, 90 psi)/at 500 r/min
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