PERIODIC MAINTENANCE 2-41
COMPRESSION PRESSURE CHECK
The compression pressure reading of a cylinder is a good indicator of its internal condition.
The decision to replace the cylinder is often based on the results of a compression test.
COMPRESSION PRESSURE SPECIFICATION (Automatic decomp. 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
* Decomp. trouble
* Valve clearance out of adjustment
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.
* Warm up the engine before testing.
Remove the related parts and test the compression pressure in
the following manner:
• Remove the seat. (5-2)
• Remove the fuel tank. (13-2, -3)
• Remove the spark plug. (2-7)
• 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.
• Kick energetically the kick starter lever about 5 times to turn
the engine.
• Record the maximum gauge reading as the cylinder compres-
sion.
09915-64512: Compression gauge
09913-10750: Compression gauge adaptor
• Reinstall the removed parts.
Standard
400 – 800 kPa
(4.0 – 8.0 kgf/cm
2
, 57 – 114 psi)
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