Kawasaki KFX400 ATV 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 maintenance records kept at your dealership should include compression readings for each maintenance service.

Compression Pressure

Standard: 1000 kPa (10kg/cm2, 142 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 nuts 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.
Install the compression gauge and adaptor in the spark plug hole. Make sure that the connection is tight.
Keep the throttle lever in the fully open position.
Press the starter button and crank the engine for a few seconds. Record the maximum gauge reading as the cylinder compression.

Tools Required: