IIRC, Yamaha built 5 valve engines for about 20 years for their 4 cyl performance bikes. Ferrari tried it in F1. Mostly abandoned due to complexity and little performance gains. The pentroof 4 valve design appears to be the standard.
Yamaha's last 5v engines were eliminated from production maybe 10 years ago. Yamaha started to abandon the concept after Rossi tested several MotoGP prototype engines. Rossi selected the 4v "big bang" inline 4 cyl. Most MotoGP engines, whether inline or V4 engines, run 4v / 4 cyl big bang engines. Yamaha R1 sportbike is a street version and the new Ducati V4 superbike is also street version of their GP design.