I think the design sweet spot varies by the engine and it’s associated components. Regardless of the engine size.
For instance, my Victory 106” in 6th gear at 80mph is turning about 3000rpm and returning about 40mpg.
That, to me, is that particular configurations sweet spot.
There’s no particular technological limit to materials or design that dictate an engines capacity. Small motors have their sweet spot, same with medium and larger motors.
Many factors contribute to a particular setups sweet spot. A Bergman 650 has one, as does a Guzzi V7, as does a Harley with a 121” setup. It doesn’t seem engine size matters. The overall design of the ‘system’ most certainly does though. People have a preference for an engine size. But that preference doesn’t necessitate a particular engine size. It’s just their preference.
I tend to like big bikes with big motors and big power. Others prefer medium sized bikes with medium sized motors and power etc. that simply personal taste and preference, nothing more.
I don’t have enough miles on the Eldo 1400 to make a claim if it’s sweet spot. I can only go by what others report. Though my particular Eldorado 1400 likely has a different fuel map and exhaust than most. Therefore, I’d ‘guess’ the sweet spot may be somewhat different as well.
Good points. Better language on my part may have been "marketing sweet spot" or "sales quantity sweet spot."
600cc sport bikes make over 100 HP. Even a so-called beginner's bike of the late 1990's, like an SV650 will stomp all the mind blowing superbikes of the early 1970's into the ground in any measure of performance.
As I noted before, a friend thought my DR650 (35 HP) was more powerful than his son's GSXR600 (100+HP).
The difference between a DR650 and a KTM Duke 690 is phenomenal!!
Preferred usage and owner desired "sweet spot" probably makes more sense as metrics than any mechanical aspect of the motorcycle.
I suspect, desired mood requirements in the owner, mandates why many people own more than one bike.
What stimulus buttons do I wan t pushed today, determines which bike leaves the garage, and which routes are selected.