Unbelievably easy way to get this;
Go to ''Time Trial'' and select either track in the ''Road America'' circuit. Go to the ''Rent Bike'' tab and select the KTM 1190 RC8R.
Start the trial and you'll find that the bike will hit over 280Km/h before you even hit Turn 1. Just keep the accelerator down for the duration of the start/finish straight and you'll pop this achievement.