I recently helped with a Harley with Screaming Eagle parts. It had, from memory a 40 mm CV carb. Over 1400 cc.
To reference the Kaw manual, an intake valve is only open for 284* out of 720* per complete cycle. One single 34 mm CV would out perform twins until probably 6000+ rpm. A single is win/win with half the fuel standoff and intake reversion.
Why did Kaw use twins? Easy. If you take the vn to redline and shift, the shift recovery is from a high rpm. With the relatively large cam overlap and the right size carb's, throttle response would suffer some. So they under carbed the vn and used twins.
The old KZ 750 had, I believe, 38 mm Mikuni's(60 hp). My '83 Shadow (68hp) had 36 Kiehin's.
edit- the reason for the airbox, is it is larger than the cylinder swept volume. 45 cu in. The atmosphere has over twice the time to fill the airbox as with an individual 'tube'.
Last edited by wmsonta; 02-03-2014 at 05:50 PM.