In 1973 in Germany the RD 250 was available only as 5-speed version (I bought it in June 1973 for 3300 German marks). But in April 1974 I went to Switzerland and there I could buy a little metal piece (Yamaha 328-18352-10) for the gearbox of my Yamaha and at home I let it exchange - from that day I had turned my 5-speed RD250 into the 6-speed RD250. Also the sprocket got changed that day to a smaller one but after a few days I changed the sprocket back to the one that was used in the 5-speed RD250 so that I could use my 6th gear as a mere overdrive gear that I liked and used very much.