compression test

If you test with the carb open, the ALWAYS test with it open. Same if you test closed. I always test 4 strokes (8 crank revolutions) noting how fast the compression comes up on the first stroke, and where it levels out on the 4th stroke. Strokes 2, 3 and 4 should be pretty similar, the first stroke is lower because you have to fill the extra volume of the compression gauge.

I typically remove all the plugs first. Generally because I am doing a compression test as part of a tune-up and will be installing new plugs. The battery and starter will be happier.

Biggest thing is to always do it the same so you can compare results over time.