I've hit a gps' d speed of 45.8 mph on my 1963 Western Flyer bike, it has 24" wheels and a 30T sprocket, the engine was new and had just over 10 miles on it and I was on a slight decline when I hit that top speed.
I have seen 9400 rpm on one of my bikes and didnt have a speedometer on it at the time so im not sure what my speed was on it, it has 26" wheels and a 34T rear sprocket, im guessing around 45mph my dadwas cruising with me on his motorcycle and said he registered a little over 45 mph while riding beside me,, but of course those cant be seen as official mph.
Both of these bikes are running the dax GenIV lowers with good port work and piston mods, with current exhaust set up on the Kulana bike I have it cruises nice at 41-42 mph with the 34T
After hitting 45.8 mph on the WF bike I have settled in on feeling plenty comfortable with top speeds 45 mph or less on my bikes.
There have been so crazy claims of people saying they hit 45+ mph running 44T sprockets and such but I dont see that happening, Arrow racing bikes run 24" wheels and 37-38T sprocket and these are very highly moded bikes with direct case induction and well buit and balanced cranks and they hit low to mid 40's on the straight when they reach their rpm plateau.
Bairdco has the highest proven top speeds here as far as Im concerned, he has witnesses that have seen what his bike was able to do and I haven't seen or heard. Of anyone else here that has done that.
And by the way my dax lower builds run comfortably smooth at max rpms and speed..... no harsh vibes with either of these engines at wot.