For the most part, the CB400F was simply an upgraded version of the 350 model from the previous year. At the time Honda's R&D department had devoted much of its resources towards automobile models such as the Civic. This meant that motorbike development was limited to mechanical changes. In order to develop the CB350F into the CB400F, Honda increased the bore and modified the cylinder head to raise the compression ratio. In a first for Honda, a sixth ratio was fitted to the gearbox. Instead of aping the styling of the bigger Universal Japanese Motorcycle (UJM) style CB750, like the 350F had, the CB400F had a more café racer look with lower handle bars, rear set footpegs and more svelte styling. It also gained one its most recognisable attributes, a swooping four-into-one exhaust system.