Bem vindo, amigo. Eu falo portugues, mais acho que seu ingles e mehor que meu portugues... entou...
In the US, the CB400F was 1975-77, although I believe there were 1978 models available elsewhere -- someone else who knows better will likely come along and chime in -- or they might have been 1977 models left over and titled as 1978. In the US, in 1978 Honda switch to the CB400 Hawk twin. All three years (75-77) in the US the bike did have a 6-speed gearbox, and the 1977 model featured pegs that were moved forward and higher bars. People here frequently try to replace the 77 pegs with 75-6 pegs (and shift linkage and brake lever -- and they work on CB350Fs too).
From the vin #, however, it looks like a 1975 (again, someone can correct me, but the first year VINs started with 10-----, second year 20-----, third year 21-----. Take a look at the pegs -- do they sit forward or behind the
bolt where they mount? And the passenger/pillion pegs -- are they mounted to a loop on the frame or mounted to the swing arm? That might help as well. It's possible the bike was first titled in Brazil in 1978 but is an earlier model.
In terms of parts, David Silver Spares has a lot of OEM and reproduction parts for these bikes. Ebay is another spot. They are getting rarer and are sought after, so some parts don't come cheaply. Some parts can be cross referenced with a Honda parts fiche to determine if parts from other models will work (especially CB350F, although those are rare too).
Hope this helps, others will likely come along and chime in...
