Id go with your first guess. Have ya spanked the carb with a screwdriver handle? Mite wanna drain the carb bowl. Let that thing sit & not be shaken up, let everything settle in the bowl. Mite be some gunk in the valve/seat, not closing off completely when the float gets to the top.
Mite be time to dump the gas outta the tank, put fresh stuff in, if that doesnt get it, try some Seafoam, if that doesnt get it, time for a wrenchin session.
You dont hafta waste the gas that comes out. Look it over, dump some in a jar. If its obviously garbage, then, its good for fire starting, added to oil its safe, in low %ages. If its not useful to you, dispose of it "right", of course.
If its just marginal, a little in the lawnmower with the Good Gas,, like that. At 60 cents a gallon,, no biggee, but a gallon O gas? Now? Im gonna try to find a use,,

Thanks for the information.  I decided, having an afternoon with nothing on the schedule, to remove the carb, diasassemble, and clean it.  Rather lengthy process (as in Step One: disassemble motorcycle) but it was worth it.  After reassembling everything and checking my work to make sure I hadn't overloooked anything, it fired up as if it was new.  Cost me some time, several skinned knuckles, and part of a can of carb cleaner.  My charming wife is now happy - which means so am I.  

Look for dirt, varnish and clogged jets.
follow the instructions in the tech section and it'll work out.

when re-assembling use socket head screws for the carb bowl, this way you can get the bowl off without removing the carb & fuel tank

Use antisieze on the bolts. Every shop should have antisieze. I cant say when the last time was I had an WD 40 in my shop.. I dont use it, but antisieze is always on the shelf,

I just fixed a bike like this.  I had to take the drain screw out of the carb float bowl and drain all the fuel out before the bike would start and run.

When I took it apart I found the float had fuel inside.  Replaced the float and it works fine now.

You could have a sticky float, some dirt in the needle, or similarly a float that likes to "sink".

verslagen1 wrote on 08/14/21 at 11:09:32:
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While that can happen, it's important for people to understand that floats don't normally just go out of adjustment.  So if the bike was running fine and then all the sudden you're having issues it's very unlikely that it's an "adjustment".  

I would start with Dave's suggestions, but if this were a used bike that someone may have had apart, then I would look at everything.  But you also need to know why the foat is out of adjustment.  Is it filled with fuel, is the valve stuck, is there debris in there???

I know varslagen1 knows this stuff, but the statement might lead a less experienced mechanic down the wrong path.