Honda CB400SF motorcycles are equipped with a mechanical six-speed two-shaft gearbox (KP) with foot switch. First gear is engaged by pushing the lever down from «neutral», other gears are engaged by moving the lever up. The design of the gearbox uses a scheme with constant meshing of gears, while the gears of the primary shaft are rigidly fixed to it, and the gears of the secondary shaft rotate freely on the shaft and are fixed on the shaft using shift clutches, thereby closing the power flow transmitted from the engine to the main gear.
The gearbox is interlocked with the engine and clutch basket in a single crankcase and has a common engine oil lubrication system. The shafts are mounted in the gearbox housing on roller and ball bearings.