this is mostly due to the fact that a motorcycle rear tyre,
being a VERY elastic dynamic model (flexing under load,
contact patch variations linked to lean angle and MOST OF ALL
power “pulses” influencing the shape of the actual contact patch
at any moment of time), is much more dependant on the engine’s
torsional-vibration-characteristics and the frequency/mode of
the power delivery pulses. The latter is MOSTLY influenced by
the engine firing order / crankpin angling, which is one of the
key reasons why top-notch racing bikes are going in the direction
of V-engines and I-3, as opposed to flat-plane I-4 etc..

Of course, there are other reasons linked to packaging, aero, mass
centralisation, reliability, and (last but definitely NOT least),
engine structural rigidity at high-RPM (as engine blocks are getting
more and more used as stressed parts of the “frame”, or what’s left of it..
(not unlike F-1 singleseaters).

As soon as an engine becomes a VITAL part of the chassis/frame load-bearing
structure (and this goes BOTH for cars and bikes..), you’d be surprised to see
how suddenly some ‘packaging’ and design issues become of FAR greater importance
than (comparatively) V.E. or friction relaed advantages that the “other” solution
has…

Bottomline: the Inline-4 (at least when mounted in a conventional position in a bike’s frame) is VERY disadvantageous for the requirements of a top-level racing bike design.
Just try to imagine how edgy it must be to control 250-ish HP at the rear tyre under extreme lean angles, and you’ll anticipate how every single aspect of the way HOW is the power delivered suddenly becomes extremely important.

AW

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Yes, I realize I’m no racer, but even Rossi calls Sepang and most other GP circuits car tracks.

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by car circuits, you mean the same ones that were purpose built to accomodate the scale of F1…?

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… said the struggling 7th grader to the math tutor.

re: “By the example I cited, “mature” riders would choose the in-line four (not the v-motor, preferred by the OP) — the in-line four makes more torque and at a lower RPM.”

except in practice this isn’t what occurs. mature riders (by definition) are neither math AVERSE nor are they inclined to just “write off” the effects of gravity.

re: “I’m with John and Todd — power characteristics are designed-in — not a consequence-of.”

then what we have here is a “hat-trick” of bad assumptions…! LOL guys, designing it in is just ONE way, not to be confused with the ONLY way.

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excellent, then this will be a “3-fer”.

re: “You can engineer any characteristic you want into an engine. Being an inline or V is immaterial”.

you (and you only) are right in this observation, statement, but what do you have when you fail to split hairs on the engineering…? what do you have as a bonus, when you’ve spec’d a configuration for an unrelated set of priorities…? ps, there are hundereds of thousands (if not millions) of engines in operation that got spec’d on only a handful of parameters. a current example that comes to mind would be mazda’s outgoing 2.2L diesel. RTL’s statement is 100% correct.

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because it’s correct.

re: “while I have come up with several things that kinda sorta make sense, I have not come up with anything that makes perfect sense.”

then you need to keep thinking is all. the answer’s there. here’s a hint, it’s not nearly as complicated as you’re making it. that’s what’s keeping you from seeing it… “you’re overshootin’ the runway”.

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unfortunately, you’re making the classic mistake of simply comparing apples to oranges. no worries, what you need is a common metric to tie those 2 models together and give it meaning. it’s starts with asking the question, “gee, how much does a busa weigh?”. i already know the numbers and the answer, but just spiting ‘em out (like most are apt to do) doesn’t really help. so what i’d like, is for YOU to complete the rest of the math and then come on back and report on what you’ve discovered. how’s that sound…?

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