Moped Army

This seems to be an odd one to me. My 1980 MC50 ran fine a few days ago. Now, after several rainy days in Florida, there is no spark. The bike got wet. Now, no spark-well, almost. I cleaned and set the points, checked capacitor and coil to be sure they are dry. Here's the odd part- when I release the starter spring with the plug removed from the head, but connected to plug wire and plug grounded, I get one solid spark every time I move kill switch or ignition key to "off", then "run".One spark each time. If I jiggle the switch or key several times while engine is being turned via starting spring, I get several sparks. But- only 1 at a time!! Any ideas?
Sounds like something grounding somewhere, but, why the solitary spark? Thanks, Ron