PERIODIC MAINTENANCE 2-27
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
Standard: 950 kPa (9.5 kgf/cm
2
, 135 psi)
(Automatic decompression actuated)
Low compression pressure can indicate any of the following 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
NOTE:
When the compression pressure goes below specification, check the engine for conditions listed above.
COMPRESSION TEST PROCEDURE
NOTE:
Before testing the engine for compression pressure, make sure
that the cylinder head bolts are tightened to the specified
torque values and the valves are properly adjusted.
Warm up the engine 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 spark plug. ( 2-9)
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 open position.
Press the starter button and crank the engine for a few sec-
onds.
Record the maximum gauge reading as the cylinder compres-
sion.
09915-64510: Compression gauge set
09915-63310: Adaptor
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