I decided to go ahead and tear down my recently acquired Rainbow E2 and clean out the motor chamber and the fan chamber. Here's the mess in the motor chamber.
And crud inside the fan chamber. The fan washer is being difficult to remove. It looks rusty, so I'm guessing the previous owner stored the motor unit on the water basin. Once I get that washer off, I think I'll just go ahead and service the motor with new bearings and motor brushes.
Forgot to add that these 1 speed Rainbows are really easy to get into and service, though I still can't quite figure out how the separator keeps water from getting sucked into the motor!