There are two compression tests that you should perform; Wet and dry. Do the dry test first.
For accuracy, you MUST perform the compression tests with the engine as close to operating temp as possible, and have the throttle blocked open. You should also do both tests at the same time, dry first.
You do not need an air compressor to do this.
In short:
1) Warm up the engine
2) Disconnect the coil
3) Block the throttle so that it is wide open
4) Remove all 8 spark plugs
5) Install the tester and crank the engine through 5 revolutions
6) Read and write down the results
7) Repeat steps 5 & 6 for the remaining cylinders
8) Add 3 squirts of engine oil into the spark plug hole of the first cylinder you tested, and test it again
9) Read and write down the results
10) Repeat step 8 & 9 for each of the remaining cylinders, but do not add the oil until you are about to test that specific cylinder. Adding oil to all of the cylinders at the same time won't work correctly.
Your numbers will be higher after the wet test. The numbers themselves aren't as important as the difference between them.
Post your results.
Take care,
-Chris
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