CHK
ADJ
CHECKING THE COMPRESSION
6. Measure:
• compression pressure
Out of specification
-->
Refer to steps (c) and
(d).
a. Set the starting switch to "ON" and the “engine
stop” switch to “
”.
b. With the throttle wide open, crank the engine until
the reading on the compression gauge stabilizes.
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.
Compression (at sea level)
Standard 1200Kpa
(12kg/cm
2,
170.7 psi)
Minimum 1050Kpa
(10.5kg/cm
2
, 152.3 psi)
Maximum 1300Kpa
(13.0kg/cm
2
, 188.5 psi)
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T
T
T
T TT
T TT
T TT
T TT
T TT
T TT
T TT
T TT
T TT
T T
T
T
T TT
T TT
T
T
T
T
3
3-17
Compression pressure
(with oil applied into the cylinder)
Reading
Higher than without oil
Same as without oil
D
iagnosis
Piston ring(s) wear or
damage
-->
Repair.
Piston, valves, cylinder
head gasket or piston
possibly defective
-->
Repair.
To prevent sparking, ground all spark plug
leads before cranking the engine.
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WARNING
Summary of Contents for YBR250 2007
Page 1: ...YBR250 SERVICE MANUAL 5D1 F8197 E0 2007 ...
Page 2: ......
Page 359: ...YAMAHA MOTOR DA AMAZÔNIA LTDA ...
