Excelsior Manxman

Predating Hondas radial four valve RFVC engines by 50 years, Excelsior experimented with both pushrod and OHC-operated layouts for a number of years before returning to conventional 2 valve engines, much like Honda did with their XR200 engine. For all the theoretical advantages of a radial valve layout, they seemed to produce no more power than a simple single intake and exhaust valve arrangement.