2-22 PERIODIC MAINTENANCE
COMPRESSION PRESSURE CHECK
The compression pressure reading of a cylinder is a good indicator of its internal condition.
The decision to overhaul the cylinder is often based on the results of a compression test. Periodic mainte-
nance records kept at your dealership should include compression readings for each maintenance service.
COMPRESSION PRESSURE SPECIFICATION
Low compression pressure can indicate any of the follow-
ing conditions:
* Excessively worn cylinder walls
* Worn piston or piston rings
* Piston rings stuck in grooves
* Poor valve seating
* Ruptured or otherwise defective cylinder head gasket
Overhaul the engine in the following cases:
* Compression pressure in one of the cylinders is less than
800 kPa (8 kgf/cm
2
).
* The difference in compression pressure between any two cyl-
inders is more than 200 kPa (2 kgf/cm
2
).
* All compression pressure readings are below 1 000 kPa (10
kgf/cm
2
) even when they measure more than 800 kPa (8 kgf/
cm
2
).
COMPRESSION TEST PROCEDURE
NOTE:
* Before testing the engine for compression pressure, make
sure that the cylinder head nuts are tightened to the specified
torque values and the valves are properly adjusted.
* Have the engine warmed-up before testing.
* Make sure that the battery is fully-charged.
Remove the related parts and test the compression pressure in
the following manner.
• Remove the fuel tank. (!4-3)
• Remove all of the spark plugs.
• Install the compression gauge and adaptor in the spark plug
hole. Make sure that the connection is tight.
• Keep the throttle grip in the fully opened position.
• Press the starter button and crank the engine for a few sec-
onds. Record the maximum gauge reading as the cylinder
compression.
• Repeat this procedure with the other cylinders.
# 09915-64510: Compression gauge set
09915-63310: Adaptor
Standard Limit Difference
1 000 – 1 500 kPa
(10 – 15 kgf/cm
2
)
800 kPa
(8 kgf/cm
2
)
200 kPa
(2 kgf/cm
2
)
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