With an experienced team and a lot of data.
Protect your 1989 BMW R100RT from the unexpected.
The G/S line was developed from BMW’s years of experience in the incredibly tough International Six Day Trials (ISDT), which they first won in 1933. In 1975, several BMW engineers built copies of the R75/5 ISDT bikes for their own use, and management felt that the model could have a future.
The BMW R80G/S was green-lighted for 1981. G/S translates to “Gelande” for off-road and “Strasse” for street. It was a genuinely new idea, as the 800 cc, 500-lb bike was considered both too heavy for-off road and too clumsy for the highway. The G/S turned out to be an admirable compromise, though, and evolved into a new class that came to be known as the Adventure Tourer.
Changes to the street model included a 21-inch front wheel, high front fender, two-into-one exhaust and the first single-sided swing-arm – the Monolever. The bike was finished in white with red and blue decals, and the instrument panel held only a speedometer and warning lights, though most dealers added a tachometer. A full engine update featured Bosch electronic ignition, improved oiling and bigger sump. Hubert Auriol won the 1981 Paris-Dakar on an R80GS – the first of many wins – and in 1984 an R80G/S Paris Dakar model was offered with a seven-gallon tank, bright graphics and solo seat.
The first redesign came in 1988 and only the 1000 cc R100 GS (no slash now) came to the U.S. A Marzocchi front fork was fitted for better control, and the wheel rims were ingeniously redesigned to fit the spokes on the outside of the rim so that tubeless tires could be used. The Monolever swing-arm was also replaced by a dual Paralever design. The GS also had crash bars, an oil cooler, a bigger starter and a battery.
The Paris-Dakar was launched in 1990 and looked like a poseur’s rig, unless you actually went in harm’s way, in which case it worked well. The headlight and number plate was replaced by a fairing with a full set of crash bars, an 8.7 gallon fuel tank was fitted with a huge skid plate, a solo seat and luggage rack with bag mounts (bags were optional). With 58 bhp, the 485-lb R100 GS could do 0-60 in 4.7 seconds with a top speed of 102 mph.
The fuel-injected four-valve “oilhead” engine appeared on the 1995 R1100 GS, with a mixture of air and oil cooling, and a camshaft under the engine to keep it narrow. The front forks were replaced by a Telelever, where braced fork sliders carried the front wheel, while a ball joint in the center of the brace connected to an A-frame whose legs connect to the engine’s crankcase. A second ball joint on the top brace linked to the frame and a coil-over shock tied the lower arm to the sub-frame. The system was extremely rigid and easy to maintain, with built-in anti-dive resistance. Four-piston Brembo discs were also fitted.
Suspension travel was increased to 7.5 inches, the front wheel was changed to 19 inches, and ABS was optional then standardized in 1998. The GS was face-lifted in 2000 and the engine bumped to 1,150 cc with a six-speed gearbox. The R1200 GS was released in 2004, saving 60 lbs weight and given 100 bhp for the first time.
There is almost nothing as tough as a GS, and intrepid explorers like Helge Petersen have traveled hundreds of thousands of miles on them to every imaginable corner of the globe. All sorts of options can be fitted, from multiple lights, heated grips, seat and foot pegs to GPS systems.
For all that, not many GS bikes are exposed to destructive conditions, and their very under-use means that good examples of all ages can be found. Don’t worry about mileage. The key to buying a good one is extensive and complete maintenance records.