Compression

Insufficient compression pressure will result in performance loss and may indicate leaking valves or worn or damaged piston rings. Procedure:

1.    Make sure the valve clearance is correct.

2.    Warm up the engine 2^3 minutes.

3.    Remove all the spark plugs.

4.    Install a compression check gauge.

5.   Turn over the engine with the electric starter (make sure the battery is fully charged) with the throttle wide open until the pressure indicated on the gauge does not increase further.

Compression pressure (at sea level):

Standard ............ 8.5 kg/cm²(121 psi)

Minimum............ 7.0 kg/cm²(100 psi)

Maximum .......... 9.5 kg/cm²(135 psi)

WARNING:
When cranking the engine, ground the removed spark plug wires to prevent sparking.

1. Compression gauge

6.    If the pressure is too low, squirt a few drops of oil into the cylinder being measured. Measure compression again. If there is a higher reading than before (without oil), the piston rings may be worn or damaged. If the pressure remains the same after measuring with the oil, either or both the rings and valves may be the cause.

7.    Check each cylinder. Compression pressure should not vary more than specified value from one cylinder to any other cylinder.

Difference in gauge reading: Less than 1 kg/cm² (14 psi)