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ADV NewsBuilding The World’s Lightest BMW R1250GS

Building The World’s Lightest BMW R1250GS

The Big GS goes through an extreme diet while still remaining street-legal.

Published on 06.23.2023

Along the vast spectrum of feelings people have about BMW’s R1250GS, there’s one sentiment that’s universal: It’s heavy. So, what would an extreme weight loss journey look like for the flagship GS? The builders at Oldtimer Middle East, based in Dubai, went on a mission to find out.

The idea was borne when customer Rob De Deken approached the shop about turning his brand new 1250GS into more of a dirt bike. According to the shop’s General Manager, Wissam Jayyoussi, De Deken’s instructions were simple, yet lofty: “I want this bike to be a KTM 890’s weight, with double the power.”

The inspo for the project would also come from BMW’s HP2 Enduro, a big “dirt bike” built from 2005-2008 that weighed just under 400 lbs. 


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The weight loss process started with a complete tear down, and by complete Jayyoussi says literally everything came apart, “every little bolt, every little cable.” The idea was to transform the big adventure bike from the inside, out, and that started with a hard look at its bone structure. 

World's lightest BMW R1250GS street legal adventure motorcycle

After a thorough examination the team decided on some weight-shaving refinements for the frame. Obviously, the center stand was jettisoned, and its brackets were also shorn from the frame. The bike’s factory auxiliary lights and all other accessories deemed unnecessary for off-road riding were likewise nixed along with their fixed mounting points. Afterwards, the frame was smoothed and refinished in a striking fluorescent lime shade.

World's lightest BMW R1250GS street legal adventure motorcycle

The subframe was tossed entirely and a new one was fabricated in-house using titanium tubes, a change Jayyoussi says shed around 10 lb from the bike. 

Another major gain came from tossing the complete stock exhaust system. Oldtimer mechanics then added an Akrapovic titanium header, even going as far to remove the internal flapper, citing how even a few ounces here and there can add up to major change in the finished product. For the canister, Oldtimer didn’t go with the expected Akrapovic part made for the GS, instead opting for the race weight slip-on built for the S1000RR GP. Yes, the bike’s loud now, says Jayyoussi, but not in a bad way.

World's lightest BMW R1250GS street legal adventure motorcycle

The GS’s conventional battery also had to go, and was replaced by an ATZ-10 lithium unit made by Antigravity, an easy, layman’s move that shaves about 5 lb from the bike. But Oldtimer didn’t just change out the battery, they relocated it forward, into the space in front of the fuel cell that normally housed the bulky air filter box. 

What happened to the air box, filters and their pipe work? Gone. Instead, the shop opted to install unhoused pod filters, which Jayyoussi claims are not only lighter than the stock, but provide more air flow as a bonus. 

World's lightest BMW R1250GS street legal adventure motorcycle

Another major change to the bike was deleting the stock suspensions and their Dynamic ESA computers. Jayyoussi says the modules alone cut around 9 lb from the bike. He reports that a Wilbers suspension setup was custom built to match the owner’s off-road riding style and weight. 

World's lightest BMW R1250GS street legal adventure motorcycle

As for braking alterations, TRW slotted MSTR242 discs were switched in saving some ounces, though it’s noteworthy that quite a bit of corrosion is visible on these aftermarket additions. 

Wheels on the bike were swapped to Takasago Excels, including a switch from the standard 19” to a 21” front rim, a good move for its off-road intentions, but not one that amounted to any weight loss. 

World's lightest BMW R1250GS street legal adventure motorcycle

Now that the major components had been addressed it was time to take a look at saving as many ounces as possible within the smaller elements. Since the bike was going to remain street legal, indicator lights were required, though the stock units were removed and replaced with Atto units from Kellerman. 

World's lightest BMW R1250GS street legal adventure motorcycle

The multifunctional rear Atto DF lights, which incorporate turns, braking and running light behind one small lens on either side of the bike allowed for removal of the tail light and bulky plate holder, too, in total, changes that amounted to over a pound of excess plastics removed. The rear plate is now fastened to a folding plate holder from Rizoma. 

World's lightest BMW R1250GS street legal adventure motorcycle

Rizoma is also the maker of many of the bike’s other bits, including the rear brake reservoir, clutch and folding front brake levers, rear brake lever, foot pegs, radiator guards and handlebar risers. 

In the cockpit, the large TFT screen remains as well as the huge structure that secures the TFT, windscreen, headlamp and fairing. Jayyoussi explains the mountain system was too complex to recreate in a lighter material, so they chose instead to cut large circular holes in the structure’s flush surfaces in an effort to shed more ounces. “It’s accumulative,” he says. “Keep in mind we were looking to lose every gram we could, so we went into every little detail.”

World's lightest BMW R1250GS street legal adventure motorcycle
World's lightest BMW R1250GS street legal adventure motorcycle

Gone is the large tour-friendly windscreen in favor of a Jetflow fly screen from Wunderlich, a piece Jayyoussi says “weighs almost nothing.” Missing also are the rearview mirrors and there’s no mention of replacements, though to be street legal in UAE, there must be a requirement. The bike’s main headlight remains and the handlebar is stock, though capped in squeezable Grip Puppies. 

World's lightest BMW R1250GS street legal adventure motorcycle

One surprising way nearly 4.5 lb was said to be shed was by simply replacing every replaceable bolt with titanium alternatives from ProBolt. All the little covers on the bike, such as the ESA access port covers, were swapped to carbon fiber clones made in house, and a side stand switch cover from Wunderlich was also added. 

Since the bike was to be ridden almost exclusively off-road, there needed to be some protections, but the team at Oldtimer wasn’t interested in conventional crash bars. Instead, just the cylinder heads are shrouded in plastic Valve & Cylinder Guards from Wunderlich. A carbon bash plate from Ilenberger protects the sump. 

World's lightest BMW R1250GS street legal adventure motorcycle

After all the weight shredding mods were complete the engine was re-tuned to perform with the new exhaust and air filters. Word from Oldtimer is the bike is now “pushing around 150 hp and 106.6 lb-ft of torque,” which would be a significant jump from the stock bike’s top end of 136 hp, while torque stayed roughly the same (stock is 105 lb-ft).

World's lightest BMW R1250GS street legal adventure motorcycle

Finally, a Rad seat and panel kit by Unit Garage was added, replacing all the stock body panels with more stylish, and slightly lighter fare. 

So, what did the scale say after this 1250 GS’s extreme weight loss program? Jayyoussi says the bike now weighs in at 463 lbs fully fueled, 88 lbs down from the original stock wet weight of 551 lb. 

World's lightest BMW R1250GS street legal adventure motorcycle

Did it match up to Rob De Deken’s ambitious dream of wanting a 1250GS that was the same as the 474 lbs claimed wet weight of a KTM 890 Adventure, with double the power? Well, that kind of power was always out of the question since output would need to exceed 200 hp to be doubled, but boy, did Oldtimer nail it on the weight. 

Tragically, the bike’s owner, Rob De Deken, was only able to enjoy his new ride for a short time, having passed just a few months after the build was finished. The “World’s Lightest Street Legal R1250GS” now lives full time back at Oldtimer, where they are thinking about moving on to a 2.0 weight reduction plan, all to honor their friend and customer.

World's lightest BMW R1250GS street legal adventure motorcycle

This next plan would mean the bike would no longer be street legal, since immediate castoffs would be the license plate holder and indicator lights. There would be one less brake caliper and disc up front, and the ABS system would go bye-bye, too. At the end of phase two Jayyoussi says the bike could end up another 22 lb lighter, so something like 441 lbs.

And while we’d all welcome the lighter weight in a flagship GS, the bike would also be a much less capable travel mount, which is the reason most choose it in the first place. But as a novelty? Who wouldn’t enjoy trying to fly this beautiful GS dream bike across Dubai’s otherworldly dunes. 

Photos by Oldtimer

Author: Jamie Elvidge

Jamie has been a motorcycle journalist for more than 30 years, testing the entire range of bikes for the major print magazines and specializing in adventure-travel related stories. To date she’s written and supplied photography for articles describing what it’s like to ride in all 50 states and 43 foreign countries, receiving two Lowell Thomas Society of American Travel Writer’s Awards along the way. Her most-challenging adventure yet has been riding in the 2018 GS Trophy in Mongolia as Team AusAmerica’s embedded journalist.

Author: Jamie Elvidge
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James Parker
James Parker
July 25, 2023 10:03 am

Very cool. Can’t wait to see the next phase of the project.

Kaptain
Kaptain
July 27, 2023 8:24 am

Very cool but I’m a bit lost on “open pods” on a dirt bike.

Dalton Goodwin
Dalton Goodwin
August 4, 2023 5:52 am

Glad someone is thinking this way. When you keep on.adding you have to subtract.

Brian
Brian
October 28, 2023 4:06 am

the person who built this bike passed away almost 2 years ago. He built this bike.. not oldtimer.. oldtimer should give the credit to that person not to themselves. Shame

Jamie Elvidge
Jamie Elvidge
October 28, 2023 10:43 am
Reply to  Brian

In the article we do talk about Rob De Deken. It’s a shame he didn’t get more time on the bike.

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