The CBX250RS was sold in the UK between 1984-6 but was not a success. The limit for learners had been reduced from 250cc to 125cc and the bottom fell out of the 250cc market.
The CBX was the replacement for the CB250RS which I owned. (see here) The main difference was that the engine had twin cams….
…..and RFVC - radial four valve combustion. In this the valves were arranged radially rather that the more usual pairs of parallel valves. This was a more hemispherical arrangement and was also used in the XR enduro bikes of the period.