Back in the early '70s, used to wheelie just about everything.
......Except BMWs.
Those things like to twist going up.
Had a beautiful blonde on back of my panhead. "Can you do a wheelie?" Not a problem, stood it up (impressive with a 20"-over springer), walked it down the road, and recall seeing a foot pass over my head, right-to-left, and the bike got lighter.
Brought it down, turned it around, there she was, in the ditch, muttering "I thought it was going to flip over!"
Took her home for some TLC.
Imagine standing one of these up.
Like erecting a telephone pole.
Learning to wheelie is easiest on the small 50-70cc stuff. Just slide back, drag your feet, hold onto the handlebars, and jerk it up. While your feet are dragging, it's easy to simply stand/run behind it if it wants to go over.
On bigger bikes, get rolling slowly, stand on the pegs, and do a spring/hop on the pegs while simultaneously opening the throttle, and it'll come up...