Compression Pressure Measurement

Submitted by xjcdadmin on Mon, 06/07/2010 - 22:56
Model(s)
750XN (MaximX)

NOTE:
Insufficient compression pressure will result in performance loss.

1.  Measure the valve clearance. Adjust as necessary.

2.  Warm up the engine.

3.  Remove the spark plugs

4.  Measure the compression pressure

Compression pressure measurement steps:

• Install the Compression Gauge (90890-03081) (1) using an adapter.

• Crank over the engine with the electric starter (be sure the battery is fully charged) with the throttle wide-open until the compression reading on the gauge stabilizes.

• Check readings with specified levels (See chart).

Compression Pressure (at sea level):

Standard: 1,059 kPa (10.8 kg/cm2, 154 psi)

Minimum: 1,098 kPa (11.2 kg/cm2, 159 psi)

Maximum: 1,138 kPa (11.6 kg/cm2, 165 psi)

WARNING:
When cranking the engine, ground all of the spark plug leads to prevent sparking.

• Repeat the previous steps for the other cylinders.

• If pressure falls below the minimum level:

1)  Squirt a few drops of oil into the affected cylinder.

2)   Measure the compression again.

Compression Pressure (with oil introduced into cylinder)

 

Higher than without oil

Worn or damaged pistons

Same as without oil

Defective ring(s), valves, cylinder head gasket or piston is possible.

Above maximum level

Inspect cylinder head, valve surfaces, or piston crown for carbon deposits.

 

NOTE:
The different between the highest and lowest cylinder compression readings must not vary more than the specified value.
Difference between Each Cylinder: Less than 98 kPa (1 kg/cm2, 14 psi)