THANKS ALBERTO for this update! 😉

SOURCE:  CYCLE WORLD

Adventure-touring bikes have been BMW’s bread and butter for years. But after pretty much inventing the segment when the company released its R80 G/S back in 1981, you could say BMW deserves to dominate worldwide sales in this fast-growing market. Over the years, competition has gotten stiffer and recent new models like the Yamaha Super Tenere, Triumph Tiger Explorer and Ducati Multistrada have really turned up the heat and forced BMW to raise its open-class adventure-tourer game.

While the R1200GS and its variants have held their own, BMW is hard at work developing and testing the aging design’s replacement. These recent spy shots showing BMW testers shaking down the next-generation GS confirm the existence of the rumored liquid-cooled R1250GS (Cycle World, Roundup, December, 2011).

That’s right, the BMW flat-Twin—after using air-cooling since the 1923 introduction of the R32 and culminating in the air/oil-cooled R1200—will feature liquid cooling in an effort to extract more power and improve efficiency.

Said Technical Editor Kevin Cameron in our print story when the new GS first broke cover: “A common cooling problem arises when engine displacement is enlarged. As bore and stroke are increased (for example, as BMW’s 500cc flat-Twin became a 600, a 750, etc., on it way to its present 1170cc), the displacement increases as the cube of dimensional change while the surface area available for cooling fins increases only as the square. As heat produced is proportional to the displacement, it is thus possible for an engine to outgrow it cooling capabilities.

“Well-executed liquid cooling does a much better job of keeping valve seats dimensionally stable,” Cameron continued,  “and it also has potential for power increases because: a) air entering a cooler cylinder expands less and thus loses less density, and b) a well-cooled head and piston can operate knock-free at a significantly higher compression ratio. Note that today’s liquid-cooled motorcycle engines typically have compression ratios as high as 13.0:1, while air-cooled engines must generally remain in the vicinity of 10.5:1. Higher compression raises torque and improves fuel efficiency, both of which are important to the touring or sport-touring riders who make up a large percentage of BMW’s customers.”

Obvious clues that differentiate the machine in these photos from the current 2012 R1200GS include intake ports that are relocated to the 12 o’clock position instead of 9, which also means that the exhausts now exit at 6 o’clock instead of out the front of the head at 3 o’clock.

Given that the GS’s design brief includes fairly extreme dirt-worthiness, it seems unlikely that BMW would try to tune the engine to meet the more street-biased Multistrada’s 134-horsepower/82 foot-pound output. Based on the last R1200GS’s 98-hp/79-ft.-lb. dyno performance, we’d expect a sizable boost into the 115-120-hp range, giving it a few more ponies than 113 hp we recently recorded for the new Triumph Tiger Explorer. With the almost certain increase in compression, peak torque will probably fall in the 85-ft.-lb. range.

Other visible changes? The Paralever swingarm/shaft final drive and exhaust outlet have swapped sides vs. the current model; a new Telelever fork has accommodations for radial-mount brake calipers; bulbous upper fairings conceal the radiators and cooling fans; and crisper styling of the windshield and the headlight assembly (which looks to be LED) update the bike’s looks.

The photos suggest that the R1250GS prototypes are in an advanced state of development with what appear to be near-production-level components. One version of the bike pictured has a heavily camouflaged fuel tank, which suggests that its shape has been finalized. In other images, the tank cowlings are poor-fitting and more representative of an earlier-stage development mule.

BMW’s only comment was that it wouldn’t comment on future product. We expect the new GS to debut this fall as a 2013 or early-release ’14  model.