Complex sentence: The RVF was originally created for the Isle of Man TT, reputedly the greatest race of mototcycles ever, the Isle of Man TT was the proving ground for Honda's new racing ability, in the form of the RVF.
Split into simpler sentences: The RVF was originally created for the Isle of Man TT, considered by many to be the pinnacle of motorcycle road racing. The Isle of Man TT was the proving ground for Honda's new racing ability, in the form of the RVF.