Horse hockey...
I don't think that's what Autoteach is talking about at all. He's been around long enough, and ridden enough, to know about torque reaction, crankshaft orientation, etc. He's worked in shops on vehicles, Mark, rather than just post on forums about 'em.
I think he's talking about one of the same things that drove me nuts on my last BMW - a 2002 R1150R, which was essentially a shorter suspension G/S - that is the weird fore-and-aft "rocking" caused by that stupidly short, highly-angled swingarm and the odd tiny bit of pro-dive that BMW built into the front Telelever to help try and make it *feel* more like a conventionally suspended motorcycle. Both made the bike incredibly sensitive to small throttle changes, and did make it rock fore-and-aft - *NOT* just side-to-side as you're trying to imply - when you make throttle changes, say in mid-corner.
IMHO it's that inanely short, moronically highly-angled swingarm that makes the friggin' things so hobby-horse pitch-sensitive. BMW can tout their horn all they want about their self-propagandized "Paralever" and make their erroneous claims that it "eliminates" shaft-drive jacking, but as with most things BMW, their claims are far, far from the truth, or reality. Yamaha employs absolutely *NO* linkage in their shaft-drive systems and they do not experience shaft-drive jacking effects. All they do is set the pinion at a low incidence angle to the drive gear and *VIOLA'*, no effects. Of course using a long swingarm helps (as it does with other suspension dynamics), but I'll leave to the collective as to which is is a better, more elegant, and ultimately more logically engineered solution.
And lets not forget that a large part of BMW's shaft drive maladies and failures are a direct result of that idiotic "Paralever", which causes insane excessive angularity issues with the universal joints, splines, etc.
It's always been apparent you would much rather own and ride a BMW (or KTM), Mark... What puzzles me is why you don't just go and buy one.
Dallara
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