Street-Legal GS Enduro Racer from SWT-Sports…
The BMW R80G/S, which helped spawn the adventure bike class and dominated several early years of the Paris-Dakar Rally, owed much to the “Red Devil” of BMW engineer Laszlo Peres — an “enduro-ized” R80 prototype Peres had been racing off-road for years. Though the G/S would gain international notoriety in the trans-Africa rallies, BMW actually won the 1980 European Enduro Championship and ISDT team gold medals on Airheads — shorter distance, more technical events.
Fast forward to present day, and there exists a community of enthusiasts who ride and race “EnduroBoxer” BMW’s — air-cooled 2-valve flat-twin Airheads built for events like the infamous Erzbergrodeo, IGE (Interest Group Endurosport) races, classic rally raids, and even vintage motocross.
Our friend Manu Schad, whose 8000-mile trip to Dakar we recently featured, is highly involved in the EnduroBoxer community, both as a racer and a builder of EnduroBoxer conversions through his workshop, SWT-Sports.
Manu himself won IGE’s “Standard Enduro” class on his race-prepped R75/6 several years ago — it’s safe to say he knows his way around an off-road 2V Boxer just about as well as anyone.
The bike you see here was built for a customer, Leon, a passionate enduro rider who was originally riding a modified R80G/S, SWT conversion no. 72. The bike had USD forks, an extended swingarm, and a reinforced frame, but not the central spring strut and Paralever conversion that Manu regards as essential for tough use in IGE races.
As many of you know, the Paralever swingarm design entered the GS line with the R100GS, eliminating the so-called Gummikuh (rubber cow) effect, which led to the suspension stiffening and bike rising under hard acceleration.
“For our boxer conversions, we use the swingarm from the R1100GS models, modified with a new shock absorber linkage point for an 18” rear wheel. Compared to the original, this is a quantum leap. The driveshaft can handle up to 150 hp, so it’s completely underutilized with our classic engines.” -Manu, SWT-Sports
After Leon test-rode one of these SWT conversions on the track, he was convinced, and a totally new build was launched, SWT no. 106 — the bike you see here.
An R100GS chassis was equipped with an SWT-Sports frame reinforcement, central spring strut with specially developed Tractive shock absorber, and a trick set of WP AER air-adjustable forks with SWT triple clamps. With this suspension setup, the bike can be tuned for just about any kind of terrain.
Though the tank is from an R80G/S, the rest of the bodywork actually comes from a Beta 300 RR. The bike is (just barely) street legal, with headlight, indicators, and instrument displays designed to be as minimalist as possible. The light and sporty bodywork make the big 1000cc 2-valve engine look all the more brutal.
Equipped with an SR Racing exhaust system, that engine makes around 65 horsepower and a stump-pulling 72 pound-feet of torque — enough guts to churn through most anything, including snow!
Basically it’s a road-legal twin-cylinder enduro racer. Manu gives us a breakdown of the riding experience:
“With the spartan seat, it’s not really suited for long adventures unless you’re prepared for some discomfort. But off-road, it performs astonishingly well. The engine, with its low center of gravity, is the perfect base for an amazing Enduro experience… Once the Enduro Boxer gets moving, it’s unstoppable! I am always impressed and can hardly imagine another way of traveling or racing.”
You can see this EnduroBoxer in action in the video above. Below, we talk to Manu for deeper details about the build.
EnduroBoxer R100GS: Builder Interview
– This motorcycle was originally a R100GS, correct? Do you know which year it is from?
Yes, the motorcycle was originally delivered as a BMW R 80 – 100 GS, but in this case, not much of that remains. The customer and I went on a three-hour Enduro ride together. Initially, it was equipped with a steel swingarm, which was absolutely outdated and took more energy than it provided.
It’s worth mentioning that at that time, motorcycles like the Aprilia RSV 450 and 550, as well as the BMW F 800, were already in use in the 2-cylinder class. After a lot of discussion, my idea eventually prevailed, and we were allowed to develop a completely new suspension. A used, new frame was purchased and reinforced, with a modified shock absorber mount.
– Can you tell us a bit about the advantages of converting to a central shock absorber?
BMW motorcycle single-sided swingarms are certainly an eye-catcher, but alongside their attractive design, they have some drawbacks. A major disadvantage is the weight. Even though the swingarm has only one arm instead of the usual two, it’s still significantly heavier. The single-sided swingarm is heavily taxed both on the road and off-road.
Initially, it was like the swingarm on the G/S and ST models. These models later became known as the “Gummikuh” (rubber cow) because they would change height with load changes: when the throttle was applied, the 2-valve engine would rise, and when the load was released, it would quickly drop back down. The central shock absorber was not really the breakthrough at the time, but the Paralever system significantly improved this driving behavior and contributed to the success of BMW’s K and R models.
For our boxer conversions, we use the swingarm from the R1100GS models, modified with a new shock absorber linkage point for an 18” rear wheel. Compared to the original, this is a quantum leap. The driveshaft can handle up to 150 hp, so it’s completely underutilized with our classic engines. For better road handling, we specifically developed and installed a TRACTIVE shock absorber.
– What was the design concept, and what influenced the build?
Design is always in the eye of the beholder. The motorcycle should appear sporty and light, but the core design elements of BMW should not be lost. We used a tank from a BMW R 80 G/S and experimented with several rear ends from both modern and classic sport enduros.
The favorite model turned out to be the rear end, fender, and light casing of a BETA 300. Today, I must say that the overall look has come together really well. I believe that BMW Motorrad could definitely appeal to customers with such a beautiful Enduro today.
– Do you know anything about the weight and horsepower of the finished model?
Weight is crucial in motorsport. Every kilogram costs more than 1000 euros. The problem with our conversions is that many of the modifications we carry out at SWT-SPORTS are not initially aimed at weight savings. We reinforce the frame with plates and tubes, install a more robust, and therefore heavier swingarm, and use a longer, more load-bearing front fork. Only the wheels and brake discs are lighter in comparison.
Therefore, we have to save weight on the engine, transmission, and other components. In the end, the motorcycle weighs around 185 kg and delivers about 65 hp with 97 Nm of torque. The sport exhaust from SR-RACING not only contributes to a significant weight reduction but also enhances the overall performance.
– Can you tell us how it rides?
This vehicle is street legal. However, with the spartan seat, it’s not really suited for long adventures unless you’re prepared for some discomfort. But off-road, it performs astonishingly well. The engine, with its low center of gravity, is the perfect base for an amazing Enduro experience. It’s powerful but not aggressive. It has plenty of pull without throwing the rider off.
Additionally, the high-quality suspension absorbs bumps cleanly and safely. What many people don’t realize is that the weight can actually be an advantage in sports applications. Once the Enduro Boxer gets moving, it’s unstoppable! I am always impressed and can hardly imagine another way of traveling or racing.
– Is there anything about this build that you are particularly proud of?
Not really. I like all of our bikes. However, this Boxer helped us develop the new milled swingarm, which, unfortunately, never really got the chance to be fully used. I personally tested it extensively in our competition Boxer. But I am very happy that I got to be involved in this bike build.
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Very nice