A modified BMW s100RR can easily reach speeds of 350km/h
And seems most reach 322km/h without much mods... google is your friend.
And you can push it further:
The same team hit 242 mph on its modified BMW S1000RR making it the fastest recorded speed ever for a BMW motorcycle. The bike was piloted by Erin Sills who broke her late husband Andy Sill's record of 221 mph at the Bonneville Salt Flats back in 2013
HA! The best bike I've ever ridden is a K5 GSX-R750, which is essentially the same bike as the K4
Like you say, not the fastest, but I swear I go faster on it than for example the CBR1000 I rode on the same day, the 750 just inspires confidence and invites you to push it to the limit, the 1000cc bikes always felt more like they're in control, not you, hence I reckon I generally go faster on the 750.
I'd look to buy something from K6 onwards though, big changes were introduced there, that is IF I ever get to own a GSX-R750.