Matt,
I don't know how you checked for piston movement. I know I cant stick something in the spark plug hole and hope to feel the piston moving on my 210. Try this, take the air cleaner off. Seal the throat of the carb with the palm of your hand. Open the throttle wide open, then have an assistant crank the engine. If you feel the suction on your palm then the piston is moving. I'm guessing something electrical got wet when you were power washing and that's why you lost spark.
Hec