"Sekiya:
On the hardware side, phased valve timing gives the engine its characteristic feel around the 3,000 rpm range. How did you create the engine's personality?
Minami:
Basically, straight-four engines run smooth as long as all four pistons move the same way. My initial thoughts were, to give the engine a deep rumble, we'd have to change the movement a bit.
We ended up shifting the valve timing of cylinders 1 and 2, compared to cylinders 3 and 4, and by continuing to change the gap, found the right combustion out-of-sync feel."
"Korogi:
At around 3,000 rpm, the four-cylinder engine vibrates strongly like a two-cylinder engine, and has a solid rev feel through the chain to the rear tire, giving a strong sense of traction, and finally a purposeful sound.
'Deep rumble' expresses the feel, through the five senses, of an air-cooled four-cylinder engine."
"Sugiura:
Of all the ideas we had for the engine's 'character,' we went ahead with phased valve timing. The engine is based on the CB1300 Super Four, and in the initial prototyping stages, we took its engine and simply modified it to be air-cooled. We had the prototype tested by a number of people, and the majority told us that it didn't feel like an air-cooled engine, that it felt the same as the 1300SF."
"Fukanaga:
I think the bike is as good as it is, because we had people in the factory see, ride, and understand the level of the engine's potential and 'feel' that we wanted.
Once the factory understood us, they started giving us ideas on how to improve the quality of the mass-produced model. This was what happened for the 2014 model."
