1975 Model Year, so starting in AUG 1974. (For MY74, the 90S had the earlier Dell Orto 38A without choke). To repeat, each European country at the time had its own definition of Model year (it was July to June in France for instance, and August to July in Germany). Which explains the recurrent misunderstanding if the US MY (matching calendar year) is followed: a "same" year seems to have a bike coming with different features. The bikes are actually two model years apart for BMW.