Re: R/K/ST/RT=Alphabet Suppe
Okay, here goes. R is for Rad, which means bicycle. BMW make aircraft engines and cars as well, you know. Early R numbers are model numbers, but later ( post '68) they indicate capacity as well, so R1100 is 1100 cc, and so on. K is for a German word I've forgotten meaning 'project', since they spent ages designing their first non-boxer engine in the early 1980s, known only by its K number, but when it was released to the public they decided to call all the in-line engines Ks: K100, K75, and so on.
ST in this case (2005 R1200ST) means Sport Touring. RT is their usual label for their fairing-and-luggage tourer: when the first R100RT came out in the mid 1970s it was said to stand for Rally Touring, i.e. going a long way and taking your camping gear with you, as opposed to the sleeker RS, or Rally Sport, where you took less gear with you and stayed in hotels! There was an earlier ST, the R80ST, in the early 1980s, which was a street-tyred version of the original R80G/S ( note the slash) where the ST stood for street, or Strasse in German. G/S, by the way, stood for Gelande/Strasse, or Off-road/Street. More modern G/s's have lost their slash and are just GS. Does that help clear the fog?