[Water Warrior 2]

If my memory still works I think I have a little info on the twin dome thing. Back in the late 70s/early 80s Suzuki was dabbling in four valve heads on their performance bikes. The technology naturally filtered down to the GZ engines and their stablemates. The twin dome heads were supposed to have a swirling effect for better mixture control of fuel and air. 2 smaller valves are lighter and flow more air than one larger valve with it's greater weight that is a limiting factor for high RPM. Modern FI in the TU 250 probably lends itself well to lower production costs with a 2 valve head and a single exhaust header pipe.
Modern FI 4 valve per cylinder performance engines have awesome power curves using shim and bucket valve adjusters. A 600 sport bike can make almost 2 times the power of my Vstrom and rev as high as an F1 race car.
In the 60s Honda had a 6 cylinder 250 for the track that was unbeatable. Tiny little low weight parts allowed it to rev to unheard of RPM at the time.