The German brand was recently spotted testing a bike that has all the makings of a middleweight F 650 GS revival.BMW clearly recognizes the potential of the burgeoning adventure bike market, and at multiple price points, too.Just a few weeks ago, the German brand was spotted testing what looked to be an M-spec version of its top-dog R 1300 GS. Between the upgraded brake hardware and other subtle changes, it promised an even more refined take on the flagship.BMW's F 900 GS might adopt a similar shape and stature, but the bike that was spotted brings some key differences. - Credit: BMW MotorradAnd now it looks as though BMW could be reviving the F 650 GS nameplate through a new middleweight offering. Spy shots recently caught test riders in Europe handling a bike that looks primed to challenge ADV steeds such as the Yamaha Ténéré 700 and Honda Transalp.Surprisingly revealing spy shotsThe bike in question was first broadly surfaced thanks to ADV Pulse. Though it's pictured partially under a cover, it's still pretty revealing due to what you can see.AdvertisementAdvertisementThat's because the shots depict spoked 21-inch front and 18-inch rear wheels, a short windscreen and an X-shaped headlight unit. You can clearly see other off-road accouterments like hand guards and a bash plate, and the bodywork is very similar in posture to rally raid bikes like the Ducati DesertX.BMW has continued to expand its adventure portfolio with bikes like the F 450 GS. - Credit: BMW MotorradMoreover, even though BMW already has an adventure-ready parallel-twin in the F 900 GS, this particular test mule shows some distinct changes. Beyond the obvious visual differences in the bodywork, the frame also appears to be adapted, suggesting a fresh engine design.Whatever it's to be called, all of these details do imply real off-road intent. The wheel size alone guarantees some degree of dirt capability, as street-going setups typically keep things more balanced.It's likely that BMW's new adventure moto will be a twin, though there's no telling how much of the engine will already be in use. - Credit: BMW MotorradThe Goldilocks size BMW needsRegardless of whether BMW goes for a 600, a 650 or even something closer to 700cc, there's a strong case to be made for adding a middleweight to its already extensive adventure bike portfolio.AdvertisementAdvertisementAfter all, long before bikes like the 450 or the 310 even existed, the F 650 GS was, in many ways, the entry point to the brand's off-road range. Smaller and nimbler than the brand's horizontally opposed R series, it's a bike that I've toyed with buying on more than one occasion (all the more so having owned and dropped an R 1150 GS). Previous generations of the F 650 GS adopted a very different look. - Credit: BMW MotorradOriginally, it was actually a funky single-cylinder model born out of a collaboration with Rotax. However, with time, it grew to not only become a twin but also much larger in displacement than its name might have suggested. The most recent version was actually a detuned version of the F 800.Across both generations, the platform proved remarkably versatile. From road-biased oddballs like the Scarver to hardcore dirt uplifts like the Dakar and Sertao, BMW has a history of flexing the F series.The Dakar version is a model that continues to have a cult following to this day. - Credit: BMW MotorradMore to comeAt this stage, we can only speculate about what BMW's unnamed adventure bike might be. However, the brand is clearly keen to explore the adventure space given its continued testing. Hopefully, it rolls out this mystery middleweight before too long.AdvertisementAdvertisementAbout the Author: Gray is an associate editor at Gear Patrol, covering cars, motorcycles and anything else with wheels. When he's not chasing the latest industry news, he's probably wrenching on one of many projects. For better or worse, he believes classics make perfectly practical daily drivers.Want to stay up to date on the latest product news and releases? Add Gear Patrol as a preferred source to ensure our independent journalism makes it to the top of your Google search results.