OOOH good opportunity for us to get a brag in!
I've been close a bunch of times. 2 heavily modified e50 I took over 45, 1 was an a55 cylinder, both ported and modified heavily. Port and build specs're on garage I think http://garage.1977mopeds.com/build/Clint%27s+old+maxi
I've had 2 hobbits also get close, on stock carb too, notched vario, except the pipes it was all just modified stock shit and they'd rip but again peak just over 45
My 2 speed sachs D would top out regularly dead on at 46. I had a regeared honda cub 4 stroke 3 speed 50 that I topped out at 46 too. Still that last 10% always escaped me.
But the only true 50/50 I had was totally cheating because I didnt do any of the go-fast engine work.
It had a basically stock morini s5, with a stock dirtbike pipe (hack/welded to fit) and a phbg19. I had that topping out over 50, fastest gps was 53. it screamed too, hell on the clutches but holy fuck it was fast and tiny.