Re: what did you do to your motor bike today?
Maybe dirt bike style rim clamps or even a couple c-clamps would do it, but that is just wierd how they would be that hard to get on. Did you use Super Tubes? (surely) Did you take the valve cores out, and press the bead up into the center of the rim when seating the last bit?
You should be able to get all but maybe 1/4 or less of the bead seated, and do without tire levers. If you need them, though, 2 plastic ones should do it, working from about 10 and 2 o clock, leaving one in place and inching the other up to it.
1" roller Dax Friction Drive and Tanaka 3300 with mods.