I have noticed certain trends in motorcycle design.
One is that three quarters of all bikes from mid to massive have a fuel consumption of 5.something L/100km. The bigger ones are up over 5.6, but even 660 singles are at 5.07 or thereabouts. Bikes like BMW's F800 or (don't laugh, it's true) Ducati's 1000DS and 1100DS air-cooled twins, with consumption figures around or even below 4, are exceptions.
Another trend is that sports tourers have settled into having weights of above 260 kg wet. 'Wet' in this case means all operating fluids and a full tank.
On the other hand, my K100RS came from BMW with a claimed fully-fueled road-ready weight of 249kg, and the its bigger-fairinged and touring-focused RT brother came in at a positively gossamer 253kg. I take those numbers from my increasingly-fragile copy of the owner's handbook - interestingly, bikez.com disagrees on the RT's weight. By contrast, Kawasaki's attempt at a cheap RT, the original and still loved 1000GTR, came in at 307kg (bikez.com).
But let's see where we're at with modern bikes (all weights from, and links to, company's websites, we may as well grant them conditional trust and let them trade creative accountancy).
BMW's closest current equivalent to the RS is the K1300S, which claims to be a sports bike but, like all Beemers (with the exception of the S1000RR superbike), makes an admirable tourer (at launch, the K1200 came in an 'S Sport' version with a sexy and RS-esque half-fairing, but sadly no longer), which claims a respectable 254kg wet. A bigger engine, more plastic and fancier suspension for only 5kg above the original sounds pretty good. The all-the-toys-but-not-a-leadwing K1300GT claims 288kg. The twin-cylinder beloved-by-police R1200RT claims a frankly surprisingly svelte 259kg (or 400kg with police gear in the panniers, I suspect). NB: BMW have built their Australian website so direct links are difficult, so sod them: They don't get any.
On the other hand, Honda's brand new and highly hyped (and ugly - my opinion) VFR1200F has a "kerb weight" claim of 267kg and the established, more GT-esque ST1300 sits at 289kg (frankly, I'll have the Beemer). Triumph's new Sprint GT, a closer comparison to these shaft-drive sports tourers than the slightly smaller Sprint ST despite its chain, claims 268kg.
Suzuki haven't quite got the hang of tourers, but the Bandit-with-a-full-fairing GSX1200FA, which isn't really sophisticated enough to play in this company, still claims a "kerb mass" of 257kg.
Yamaha's famously potent FJR1300 claims 291kg "with 25.0 litres of fuel", which happens to be the tank capacity, putting it in GT company. Kawasaki's current, king-of-the-engine-hill-and-we're-going-after-BMW-levels-of-technology-too GTR, the 1400GTR (interestingly, they don't have a "touring" section on their website and put it in Sport) claims a whopping and all too believable 304kg with a full tank and no panniers.
Most of the Italians no longer do this sort of sports-tourer, preferring to pursue the adventure-tourer style (Ducati Multistrada, Benelli TreK) but the Moto Guzzi Norge GT (PDF link, for the stats) lists a dry weight of 257kg, which puts it up near 290kg wet.
Even Honda's baby tourer NT700V Deauville (Doughville, Dulls-ville ...) with its built-in panniers comes in at a decidedly non-middleweight 257kg.
The cynic may point at all these similar-ballpark figures and suggest they're keeping more of an eye on other people than on possibilities, and an engineer may say there are only so many techniques you can use when you want to build a bike with that capacity and that level of ride comfort and weather protection without going totally overboard on costs.
But: Why? When the first K100RT came in under anything comparable today, and the RS ditto, where has it all come from? One answer is bigger engines, one answer is more plastic in the fairings, and the becoming-standard ABS hardware weighs a little, as well. On the other hand: 20 years of development.
Now, the original flying brick Ks had an aluminium engine that did most of the structural work, and an aluminium tank. Were BMW cleverer then than they are now? Did they decide the effort put into an aluminium engine block wasn't financially viable, worth it or the best engineering solution as power outputs climbed?
Or is there a "good enough" guide that even the famously individualistic engineers at BMW follow?
Which would be a great pity. My partner wants to stay with shaft drive motorbikes because she's sick of oiling, checking and adjusting chains, but wants something lighter than the RS without sacrificing power. Clearly, that's going to be difficult if not impossible and the best option seems to be a BMW F800ST, which has a low-maintenance belt drive and the same claimed power output as the K but 40kg less mass. And much more sex appeal.
And unlike cars, which have bloated with airbags, crumple zones, side-impact anti-intrusion beams, heavier laminated windscreens and a general increase in size of car and wheels, bikes haven't really added that much except cubic inches and ABS. So, clearly, experience and improved technology have not translated into net weight savings.
What I want is a shaft-drive, 1Litre semi-faired sports tourer for about 200kg. Clearly, I'm not going to get it. My best bet will probably be either an it-can't-be-can-it? 229kg R1200GS or sticking a windscreen on a 223kg naked R1200R, and no naked bike has ever looked good with a windscreen bolted on.