MADisher,
If you want to see someone FLY on a 125, you need to see my 14 yr old in action. He rides a basically stock RM125 (reeds, jetting, silencer), revalved by TrakControl, and he is one fast guy. For the season, he won the 200A Enduro season title and finished 7th overall (A & AA classes combined). Also, he is currently leading the 200A Hare Scrambles. Last year, I think two of the guys moving to AA class rode 125 motobikes. It can be done. :)
Myself, a 125 would not be for me; not enough grunt, but I DO like the light weight. I'll take the 250 motobike, please. :cool: