Have the engine at operating temp.
Remove all the spark plugs - number the wires so you get them back on right.
Remove the coil positive wire.
Block the throtle wide open.
If you have a battery charger put it in the battery before you start.
Screw in the tester.
Crank the engine so you get six full compression strokes on each cylinder you as you test it.
Write down the numbers as you test each cylinder.
Use a diagram to keep track of which cylinder each pressure belongs to.
The check valve in each compression tester is different - it would be rare to get the same reading from two different testers so concern yourself with how even the numbers are - not how high they are.
difference between a wet and dry test is also important, if compression raises significantly on a re-test with a squirt of oil in the cyl. the rings may be suspect, keep an eye also on how quickly the compression goes up on the gauge
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