It warmed up some and the ice melted in the tank. More than a few silver-dollars, there's a lot of water, like 8oz. Had a hard time figuring out how to remove the tank. Then removed the seat to investigate and discovered the seat and tank are one plastic molding. Four bolts and it was off. Good.
Strangely there was NO gas in it, pretty much pure water.

Having it off, I decided I now wanted it 100% dry, might as well. I had brought a blow dryer just in case, and it turned out to be just the right tool for the job, set on "low". Ran it on the generator.
Motorcycle inner tube, and a piece of scrap pipe for 'exhaust'.
I thought about the warnings but couldn't make any sense of them. In this case, there's no raw fuel, and once evacuated for one second, there's no vapor either. If this was dangerous how could anybody survive putting raw fuel into a tank (in the old days - the vapor billowing out). As happens 24/7/365 in half a million gas stations across the country, and with "reasonable" safety.
Hanging upside down so weight of blow dryer holds the duct open. I let it run for 45 minutes.
It worked great. I ran it until the tank felt warm on the outside. Not a drop inside remained. Last time it was licensed was 2009, but not sure how long it has sat. The carburetor was spotless inside, even though there was water in it. Surprising. Put it all back together and it runs, ready to ride!