There is more to it than just Cd, but in the case of bikes that's the big thing hurting us. I'm afraid I'm not enough of a physicist to give you the full skinny on it all.
As for the limiter, no, all bikes do not have a limiter any more than all cars have a limiter. As far as I know, the S3 does not have a limiter other than the rev limiter, and the bike cannot reach that in top gear with stock gearing due primarily to aero drag.
Of course some bikes do have limiters, just not in this particular case.
'06 Speed Triple
'96 Adventurer Cafe Racer
and a bunch of other stuff
If everything seems under control, you're just not going fast enough - Mario Andretti