I think it has more to do with aerodynamics and traction than power. At that speed it just becomes hard to find traction to overcome the air resistance. That's why those bikes peel knobs off the tires, especially on pavement where they get really hot. I noticed my bike gaining R's and the back wheel going a little sideways at about 90mph when I sat upright out of a tuck at full throttle, on a hard-pack dirt road with a little sandy dirt on top. Puckered my sphincter, for sure!