Posted April 3, 2007   Email   Print

BMW's G Series offers three new twists on the company's singles focus

By Denny Lee Thrush
Photos by Kevin Wing

People have been using versatile dual-sport bikes as the platform for home modification projects for years. Strip off a little weight, add some off-road components, and you've got a real dirtbike. More recently, many owners have gone the opposite route, replacing wheels, tires and brakes on their dual-sports to create their own Supermoto-style streetbikes.

Now, BMW has done the deal for you. Starting with the same liquid-cooled thumper engine, five-speed transmission and steel tube frame, BMW has built three new models to fill out its newest line of motorcycles, the G Series.

On the dirt-to-asphalt spectrum, the G Series starts with the G 650 Xchallenge, which is still street-legal, but is the most off-road-capable with additional suspension travel and a 21-inch front wheel. Falling into the dual-sport range is the G 650 Xcountry, which BMW describes as the perfect bike for "wandering." Finally, the G 650 Xmoto goes the street-legal Supermoto route by taking the same 652cc platform and ditching the spoked wheels for 17-inch street tires mounted on cast alloy wheels (see sidebar, right).

All the G Series bikes start with an improved version of the single-cylinder engine, designed by the Austrian firm, Rotax, that powers the current F650 line of BMWs. Like the original F650 that emerged in the late 1990s, the G Series BMWs are built in partnership with Aprilia.

The Rotax single always was more eager to rev than most 650-class thumpers, and that tendency has been enhanced in the new G Series with lighter engine components. BMW claims the engine produces 53 horsepower at 7,000 rpm and 44 foot-pounds of torque at 5,250 rpm. Electronic engine management and fuel injection, along with a three-way catalytic converter and an oxygen sensor in the exhaust, enable the X bikes to meet strict European emissions standards.

The engine mates to a five-speed transmission and the rear wheel is driven by an O-ring chain. BMW shaft-drive purists will have to stick to the company's R and K lines.

The frames are also the same on all three bikes: a combination of a steel tubular frame with a bolt-on aluminum rear frame. Like the current F650GS, the X bikes carry fuel in a tank under the seat. That's good for centralizing weight, but it does limit capacity to 2.5 gallons. The design of the tank, with the filler on the side below the seat, also means you have to have the bike leaning on its sidestand or gas will spill out when you try to fill the tank.

The wheels are the most immediately visible difference between the three models, but there are also tweaks to the suspension, to suit each bike's mission. The inverted fork up front is the same externally, but offers additional travel and adjustment on the Xchallenge and features different spring rates, depending on the bike.

The rear shock on the Xchallenge is even more unique. It uses an air damping system nearly identical to the one on BMW's big-dollar, boxer-powered off-road machine, the HP2.

There is no conventional spring. The construction is similar to a hydraulic shock, except that it uses air instead of fluid (photo left). As the piston moves inside the unit, it forces air through plates to create the damping effect. BMW say the system offers several advantages over typical hydraulic shocks, including more resistance to overheating, smooth operation and simple adjustments.

The Xchallenge comes with a hand pump that can be used to adjust the preload. The other two models have a more conventional hydraulic shock and spring.

The two models designed to see dirt action share the same brakes, but the Supermoto version of features a larger disc up front for more braking power on the street. But the bigger news is BMW's continued commitment to anti-lock brakes, even on its entry-level models like the G Series. BMW's latest version of ABS, built by Bosch, is an option on all the G Series bikes. It's the same system that's also available on BMW's other new line, the F Series vertical twins, as well as on the R1200S, BMW's sportiest boxer twin.

BMW says the ABS system adds just 3.3 pounds of weight and provides the best brake pressure modulation yet. The ABS can be switched off for off-road use, which BMW recommends. The ABS is meant to be used on pavement.

That's the hardware overview. To see how it all works, BMW cut us loose on the X bikes over three days of riding on the street, on dirt roads, and even some rocky trails in the Tucson area.

Starting out with the Xchallenge, we hit some trails. Even before the going got tough, I appreciated some of the upmarket items fitted to the bike, such as the Magura levers and the tapered handlebar, which are standard items on all three X bikes and create a look of quality.

The Xchallenge will present a challenge to riders who aren't tall. With a seat height of 36.6 inches, I felt a lot more comfortable after I adjusted the rear pre-load with the air damping system. That allowed me to get toes down on both sides of the bike. But it's important to get the rear adjustment just right, or else the bike bottoms out in rough terrain and that leads to the rear fender getting damaged when it comes in contact with the rear tire.

BMW says the Xchallenge (left) weighs in at 318 pounds, which is not particularly light for a motorcycle touted as an enduro machine. But on the other hand, it's the lightest BMW in the current lineup, and maybe ever.

Because of the weight, the bike feels slow to steer at low speeds, but the faster the speed, the better the Xchallenge feels. Wick up the pace and everything starts working the way it should, while the ride is impressively smooth.

With the price toeing the $9,000 mark, the Xchallenge is an expensive choice for off-road riding, and you'll have to decide how you're going to feel about the inevitable trailside tumble scratching up your BMW.

Switching to the milder Xcountry (right) is a bigger change than you might imagine, considering how many parts it shares with the Xchallenge. But the Xcountry is aimed at an entirely different experience.

While BMW's press materials refer to the Xchallenge as "an uncompromising off-road machine," it calls the Xcountry a "modern interpretation of a scrambler." It's a bike designed to perform well on pavement or dirt roads.

The softer focus is apparent as soon as you sit on the Xcountry, with its 33.1-inch seat height. Where the Xchallenge is serious, the Xcountry is just fun.

On dirt roads, the Xcountry feels both stable yet light of steering. Take it onto the two-lane asphalt and it feels equally at home. The 652cc powerplant puts out plenty of power for the highway, but stays smooth.

Even though it weighs a few pounds more than the Xchallenge, the Xcountry handles easier, in part because the lower seat height makes you feel like you're sitting "in" the bike, instead of perched high on top.

When it comes to the two dual-sport X bikes, maybe the biggest difference is perception. Because the Xchallenge is meant for serious off-road use, it seems heavy, even though it's about the same weight as its G Series siblings. But keep in mind, the Xchallenge is really a dual-sport bike. Most of the off-road competition is not street-legal.

By comparison, the Xcountry is more of a traditional dual-sport. It's not something you'd expect to take on a seriously difficult single-track trail, but it excels at being an all-around versatile bike to ride.

By giving you two dual-sport choices (in addition to the asphalt-only Xmoto), BMW lets you decide just how much dirt you want to take on.

© 2007, American Motorcyclist Association