The HONDA CB400F was first introduced in the fall of 1974 (model 1975). Its predecessor was the little CB350F, which was no great successtory.
In the short period the CB400F was marketed it became a popular model: over 100,000 units were produced in 3 years.
With the introduction of the CB400F the F also stood for a 4-in-1 exhaust. The CB400F is particularly known for its well shaped 4-in-1 Exhaust header.
Besides regional and color changes there have been basically 2 versions of the CB400F.
The first has 'Active suspension'. The pillon footpegs are mounted on the rear swing arm.
Thus the pillon can actively assist the rearshocks, which can be useful as the standard shocks are slightly to soft.
The second version has the pillon footpegs mounted on a(n) (extra) frame pipe. This version was only produced for the European market (European direct sales, England, France, Germany, Sweden). It was introduced in 1976 as a CB400F model and it was also applied in the CB400F2.