Nice article in Cycle News about the Honda's 1965 five cylinder 125cc racing machine. http://magazine.cyclenews.com/i/720681-cycle-news-2016-issue-34-august-30 Just keep adding cylinders and more gears into the gearbox until you win. A lot more detail about the old racing Honda's here http://www.deejay51.com/honda_hall_racebikes_Pg_2.htm Note the 1962 RC163, the engine is a 250cc four cylinder, four valve DOHC with gear driven cams. The engine produced 46PS at 14,000rpm and incorporated a six speed transmission. They weren't water cooled but still the ancestor of the MC22.
One of a kind sound. Oh boy it would be loud in a studio! Note that the bike has the normal shift pattern, not a 'race' pattern.