3 - 21
CHK
ADJ
MEASURING THE COMPRESSION PRESSURE
7. Measure:
• compression pressure
Out of specification
→
Refer to steps (c)
and (d).
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a. Set the main switch to “ON”.
b. With the throttle wide open, crank the
engine until the reading on the compression
gauge stabilizes.
WARNING
_
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
engine of oil into the spark plug bore and
measure again.
Refer to the following table.
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Compression pressure (at sea
level)
Minimum
1,218 kPa
(12.18 kg/cm
2
, 173.2 psi)
Standard
1,400 kPa
(14.00 kg/cm
2
, 199.1 psi)
Maximum
1,568 kPa
(15.68 kg/cm
2
, 223.0 psi)
Compression pressure
(with oil applied into the cylinder)
Reading
Diagnosis
Higher than with-
out oil
Piston wear or
damage
→
Repair.
Same as without
oil
Piston rings,
valves, cylinder
head gasket or pis-
ton possibly defec-
tive
→
Repair.
Summary of Contents for 2004 YP400
Page 1: ...2004 YP400 S 5RU1 AE1 SERVICE MANUAL ...
Page 2: ......
Page 8: ......
Page 9: ...GEN INFO 1 ...
Page 11: ...GEN INFO ...
Page 28: ...SPEC 2 ...
Page 30: ...SPEC ...
Page 77: ...CHK ADJ 3 ...
Page 137: ......
Page 138: ...CHAS 4 ...
Page 210: ......
Page 211: ...ENG 5 ...
Page 286: ...COOL 6 ...
Page 288: ...COOL ...
Page 299: ...FI 7 ...
Page 301: ...FI ...
Page 342: ...ELEC 8 ...
Page 378: ...8 34 ELEC LIGHTING SYSTEM ...
Page 404: ......
Page 405: ...TRBL SHTG 9 ...
Page 415: ......
Page 416: ...YAMAHA MOTOR CO LTD 2500 SHINGAI IWATA SHIZUOKA JAPAN ...