I left our Honda EU2200i generator out in the rain and it wouldn't start. This wasn't a crazy torrential rain and the outlets were on the leeward side so I thought it would be OK with the extensive plastic shrouding but I guess not and I will try to keep it mostly dry in the future.
To troubleshoot I took of the big side panel (for oil changing and air cleaner access) and things looked pretty dry in there. I also suspected the kill switch so managed to get my multimeter probes on the contacts there and it made and broke contact appropriately. A peek in at the spark plug showed it was all dry (didn't actually pull the spark plug). I pulled off the end panel on the outlet side and there was water pooled on a few components there...probably the problem even though many things are potted. I blew into all of the various outlets. Removal of the outlet plate itself showed very minimal water inside of there.
But still it wouldn't start. Twice it sputtered for one second to taunt me.
Then I tried slamming the whole unit into the floor from 2-3 inches up. It has pretty good shock absorbing feet so this didn't even jostle the generator that hard, but it fired right up after that! So I guess a few drops were shorting out something (likely in the kill switch circuit) and the abrupt movement shook them loose.
BTW when we run the generator there the exhaust gasses can swirl around behind the dodger so we keep the companionway fully closed. And there are some small cracks there but our dorades and the overall suction on the back of the dodger should keep air flowing outwards through those cracks, plus we would not sleep with it running.