Small Engines (Lawn Mowers, etc.): Comression Ratio, cylinder volume, weird question

Question
How to determine the compression ratio (anaytically and experimentally)

Answer
Compression ratio is ratio of the difference between cylinder volume at  bottom dead center and cylinder volume at bottom dead center. That would be the analytical answer.
I guess the experimental?? way would be fill the plug hole with water when engine is at BDC and turn crank to TDC. Measure the water that came out and you have your ratio.
Weird question dude.
Did you mean how do I do a compression test on my small engine. If so put your finger on the plug hole and crank the engine. If the engine pushes your thumb of off the hole you have compression.