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BMW R 100RS

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Make Model

BMW R 100RS

Year

1984 - 85

Engine

Four stroke, two cylinder horizontally opposed Boxer, 2 valves per cylinder

Capacity

980 cc / 59.8 cub in.

Bore x Stroke

94 x 70.6 mm
Cooling System Air cooled
Compression Ratio 9.5:1
Lubrication Wet sump

Induction

2 x Constant depression carburettors, Bing 94/40/105 - 94/40/106

Ignition 

Battery ignition
Alternator Bosch 12V/240 W
Starting Electric

Max Power

51 kW / 70 hp / @ 7000 rpm

Max Torque

76 Nm / 7.75 kgf-m / 56 ft-lb @ 6000 rpm
Clutch Dry single plate, with diaphragm spring

Transmission 

5 Speed 
Gear Ratio 1st 4.40 / 2nd 2.86 / 3rd 2.07 / 4th 1.67 / 5th 1.50:1
Gear Ratio Sport Version 1st 3.38 / 2nd 2.43 / 3rd 1.93 / 4th 1.67 / 5th 1.50
Rear Wheel Ratio 1:2.91 or 1:3.00
Bevel / Crown wheel 11/32 teeth or 10/32 teeth
Final Drive Shaft
Frame Double sown tubs, dual cradle

Front Suspension

Telescopic fork with hydraulic shock absorber.

Front Wheel Travel 200 mm / 7.8 in

Rear Suspension

Long swinging arm with adjustable strut.

Rear Wheel Travel 125 mm / 4.9 in

Front Brakes

2 x ∅260mm discs, 2 piston calipers

Rear Brakes

Simplex ∅200 mm drum
Front Wheel 2.15 - B19
Rear Wheel 2.50 - B18

Front Tyre

3.25 - H19

Rear Tyre

4.00 - H18
Dimensions

Length  2130 mm / 83.8 in

Width    746 mm / 29.37 in

Height   1300 mm / 51.8 in

Wheelbase 1465 mm / 57.67 in
Seat Height 820 mm / 32.3 in
Ground Clearance 165 mm / 6.49 in

Wet Weight

230 kg / 506 lbs

Fuel Capacity 

24 Litres / 6.3 US gal

Consumption Average

4.8 L/100 km / 20.8 km/l / 49 US mpg

Standing ¼ Mile  

13.9 sec / 157 km/h / 97.3 mph

Top Speed

196 km/h / 121.5 mph
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STAND BACK AND LOOK AT THE BMW R100RS.

What do you see? A super-zoomy high-kinetic roadster, for low-altitude zig-zag missions down your favorite curvy road? If you see this, your eyes have just deceived you, because under the racy packaging resides a basic long-haul BMW, the boxer twin that re-draws road maps to three-quarter scale. To see the real R100RS you must look at it with your brain as well as with your eyes; that's the way BMW designed it.

More than five years ago BMW began with the R100RS putting the motorcycle rider inside an envelope, and only recently have some Japanese makers followed suit. There are two poles in the factory-fairing business. One stresses rider comfort and protection above all; it gives the rider armchair seating with the accommodations of a small hotel. The other pole emphasizes efficient streamlining; the primary objectives are low wind resistance, unimpaired high-speed stability and minimal response to side winds. The logical extreme would be a road-racing fairing, which positions the clinch-jawed rider almost face-down over the tank. The RS falls closer to this second pole: in the interest of streamlining, the rider must fold down slightly to meet the machine, although BMW's brand of efficiency and rider comfort eschews the monkey-hugs-a-broomstick posture favored by some flashbike makes. The RS fairing provides room for clock, key and voltmeter; those who want 747 flight-deck instrumentation should go elsewhere.

The RS envelope style has its imitators, especially now, as Japanese manufacturers attempt to include fairings on high-performance motorcycles neither specifically nor solely aimed at touring: the Honda CBX Pro-Link, the CX500 Turbo, and the Yamaha 650 Turbo are three examples. The BMW's engine design lends itself to enclosures. The fairing surrounds the engine crankcase, but for the most part the air-cooled cylinders fit outside in the airstream, and away from the rider's legs. Consequently, once the bike is under way, relatively little heat gets transferred to the rider's torso. Instead, only the lower portions of the rider's legs get direct heat blast. At a standstill the engine/fairing heat thermals do rise to warm the rider, yet the effect is less than with four-cylinder or water-cooled engines. The RS fairing's sidewalls sweep back far enough to meet the rider's knees and lower legs, keeping them out of the breeze.

There's one stoplight drawback to the RS-packaged Beemer: full-stop balancing means sliding aft slightly so your shins miss the trailing edge of the fairing around the cylinders; it's that or develop a knock-kneed approach to balancing. BMW has not changed the RS in any fundamental way since it appeared here in 1976.

The RS fairing, developed in wind tunnel tests, was supposed to improve steering and resistance to sidewind forces, reduce drag, and provide reasonably complete rider protection. Factory tests showed that the RS, compared with the S-fairing BMW, had less side-wind sensitivity, lower overall drag, and increased front-end down force.

Your brain must accept these gains in efficiency as significant and important; otherwise the R100RS seems like an expensive way to break the wind and not always the most comfortable one. The rider's anatomy and preference, of course, may reject the RS seating. Some of Cycle's testers who prefer lean-into-the-wind seating see little compromise in the fairing or seating position. Shorter staffers, and those who prefer armchair seating, see the RS as a problem: too much weight transferred to hands and arms; too much strain on neck muscles; not enough wind protection for the helmet. The complaint most heard was that a kink sometimes develops in the upper-middle shoulders after long hours riding.

Aside from this, the fairing provides good protection from the elements. Nestled behind the cockpit—or, perhaps more correctly, into it—the rider's hands, arms and torso are completely shrouded from the wind. There's less pressure at the rider's back than the norm with taller fairings. The airstream over the windscreen hits at mid-helmet and causes only slight buffeting, far lower, for example, than the bluster coming off the Honda CBX fairing. If your full-coverage helmet has a leak on the face shield's lower edge, you'll get a draft running into your helmet.

Footpeg positioning is good for a wide range of body sizes. The adjustable passenger pegs can be arranged to provide more foot space for both parties; or passenger pegs can be located nearer the rider's footrests, in order to give solo riders more foot and leg positions on long rides. Only the handlebar drew flak: nearly everyone, even six-footers, thought it a touch loo low for anything less than helmet-lifting 80-mph speeds. Though we could quarrel with the bars, the seat proved beyond reproach. Its long, broad shape and its foam composition are excellent. A non-stop day in the saddle causes no numbness or pain.
Passenger accommodations, too, are designed for comfort over the long haul. The passenger benefits from the seat's good foam composition, and a small hump at the rear helps prevent sliding rearward under acceleration. The seat-to-pegs relationship produces a non-cramped, relaxed seating position and plenty of leg room, even for tall riders. For normal cruising there's enough foot room for both travelers; only at foot-down stops are the rider's feet likely to disturb the passenger. The suspension quality also makes nonstop travel easy for the RS rider. The ride is simply first-rate, erasing expansion joints, potholes, dips and humps and the irregularities disappear without clapping the suspension against its travel stops. From the saddle, all's plush. Whistling through gentle comers with cross-winds blowing, even as the speedo indicates 20 or 30 notches on the go-to-jail side of 55, the RS has a reassuring stability. And comfort, adding to the sense of well-being in the cabin.

The RS likes brisk, gentlemanly speeds, but nothing in the unseemly adolescent range. Push hard enough to threaten to ground its undercarriage, and the BMW's limp springing and damping show themselves. The RS will wallow a bit over bumps. The soft rear suspension also allows the bike to do the old drive-shaft throt-tle-and-roll-off up-and-downs. This can be disconcerting when you're going into a corner on trailing throttle because the bike will drop on its suspension. The stand tangs drag on the left, and the rear brake pedal hits harshly enough on the right to unload the rear wheel. A little reminder that it is, after all, a touring machine with some sporting pretensions, rather than the other way around.

Considering the BMW's princely bottom-line, you'd have every right to expect that BMW would equip the RS with adjustable suspension units, front and rear. That would be in perfect keeping with the BMW disposition toward things of functional value, as opposed to winky lights or more deliberate gadgetry. Thus far, BMW has resisted, other than making the Nivomat rear suspension units (see Cycle, March 1981) a $374 option and these adjust themselves. Perhaps the German engineers believe the BMW already has optimized suspension for their touring bike, and there's no use kidding anyone that dial-o-matic suspension will transform the Beemer into anything else. Besides some dummkopf would probably misadjust. Still, it's hard to accept paying all that money for a non-adjustable bike.

Coaxing the BMW up two-lane mountain passages requires some assertive twisting on the high-effort throttle grip; it demands firmer action than most. The low, short bar offers only slight leverage, but the rider can lean much weight on it. After a while the strenuous effort of negotiating tight, twisty roads takes its toll: your right hand tires. At this point you tell yourself adolescent behavior ill fits a gentleman.
Passing traffic on uphills sometimes requires two downshifts to get the tall-geared transmission down to the engine's pulling power. There's no particular afterburner effect; the engine simply builds power steadily. After passing the 4000-rpm mark, the RS has more than ample power for even narrow-road squeeze plays.

This motorcycle can cruise all day with its speedometer needle nerfing the 85-mph peg. Long-legged gearing lets the engine doze at what seems like fast idle for 55 mph. With a 190-pound rider aboard, the engine easily pulls redline in top gear, demonstrating that the gearing isn't unre-alistically high. The engine's low-frequency high-amplitude vibration rumbles the bar, footrests, tank and seat—but never all at once. The subdued and almost subliminal vibes reaching the rider are no more than a friendly murmur. In fact, the engine's throb amplifies the bike's relaxed, composed nature. You couldn't imagine a BMW with a high-intensity, anxious-sounding engine.

Lots of small details suggest that the BMW has been designed and refined by engineers who ride motorcycles. The levers form-fit the rider's hand and fingers. The controls have clean, distinct points of engagement/disengagement. The clutch lever has light pull—a model of motorcycling excellence—with positive and predictable slide-in. The front brake lever is shorter than most, but unless front-wheel stoppies are your specialty you'll need nothing more. Its firmness tells the rider everything he needs to know about braking with the preciseness of the other controls. Squeezing maximum stopping from the brakes requires a strong four-finger grasp on the stubby lever. If the brakes have a fault it is this heavy lever pressure required to extract the last bit of braking force. The rear disc brake matches the front: powerful and controllable.

Shifting action on our test bike alternated between absolutely slick and notchy. The gearbox, with its longish throw, likes deliberate foot movements at the lever. If casual, by-the-way dabbers let the transmission hang between gears, false neutrals can appear. Often our test bike was reluctant to slide into first just after being started. The bike had to be rocked back and forth and reclutched; then first finally engaged, smoothly and without a lurch. We attribute some of this reluctance to the transmission's 90-weight gear lubricant and cool weather; our false neutrals and I'm-not-home firsts showed up less frequently when the engine was warm.

Even so, our test bike's elusive gear shifting was not typical of other BMWs we've ridden. Here's another atypical point. RS riders need good necks. The fairing-mounted mirrors give a narrow view of neighboring lanes; only a combination of twisting, craning and arm lifting will reveal what's directly behind. That was annoying—but worse, the mirrors showed blurred images at almost all road speeds. The RS needs better mirrors and, for the price, the rider deserves them.
Horn button, beam switch and turn signal switches are stacked vertically. All can be used conveniently with little hand movement. The single exception is the right signal switch. The switch has nice positive detents, but you must break your grip to turn it off, especially if you're wearing heavy gloves. The bar-mounted choke lever has two stops and can easily be adjusted from the saddle.

The steering-stem-mounted damper (with 0-1-2 positions) gives barely noticeable resistance on its first position, and very firm resistance on the second. We didn't use the damper much; the RS's stability never required it. The RS has gasoline range to keep a rider in the saddle for over five hours, at which time the rider will find himself nearly 300 miles from home. The RS typically had 230 miles on the trip odometer before hitting reserve. Our mileage figures, however, don't reflect the RS's potential; the RS cruised so comfortably that no one held it to 55 mph. Our best average was 55.1 miles per gallon. Our worst, with stretches of over-85-mph runs, was a remarkable 45.0. The lockable screw-type gas cap has a hinged handle that folds flat and a slip-collar to prevent overtightening. Chances are you'll never notice spill-over from over-fill seepage. The gas tank's filler neck has a trough around it with a bleed hose to send any spilled or leaking fuel to the ground.

Under the flip seat you'll find generous space for tool kit and manual, and you'll find a tire pump, a nice-sized storage tray and a catch to lock a helmet. The tool tray lifts out to expose a locking cable stashed in the frame's main backbone. The keylock seat can be left unlocked. Although the fairing has no storage compartments, the saddlebags, now a part of the RS package, are large enough to house a f uN-coverage helmet; they are rated at 22 pounds each. They attach in a snap, locking in place with a single latch at the rear of each bag. When these bags are mounted, the seat can be lifted only enough to lock a helmet; the right bag must be removed for complete under-seat access.

These 20-liter trunks have enough room to keep the light traveler on the road for a long time—or to provide the short-ranger with lots of space for office or work-type items. Each bag measures roughly 17x12 x 8 inches, with additional space in the oddly shaped area that bulges behind, inside the mounting rack. On the bike they measure just 31 inches across, only a couple of inches wider than the width of the bike across the cylinder heads. Inside are handy elastic straps to help locate the load and a hinged stop to hold the lid open horizontally. These hinges can be unsnapped to allow the bags to lie flat for packing. BMWs aren't unbreakable. The center-stand foot-tang on our test bike broke off early on, and the sidestand tang bent up under the muffler after grounding on corners a few times; this left the bike frustratingly propless. The tang on the soft aluminum sidestand was straightened, re-bent and straightened again

Those who do their own servicing should prepare to be bored. The low-maintenance shaft driveline, breakerless ignition and 5000-mile recommended service intervals leave little to the home tinkerer. The clearly written and illustrated owner's handbook plainly outlines oil changes and tappet adjustment the only regular maintenance. All these normal chores can be accomplished with the well-equipped tool kit.

We spent more hours and more miles behind the RS's cowling than on any bike we've had around our office in a long time. Of course, those staffers whose 150-deci-bel riding style reduces footpegs to nubs usually bypassed the RS; others preferred the RS those who enjoy its composed nature, its swiftness over long distances, the crispness of its controls, and its full-fairing shelter without crpss-wind susceptibility.

Seven grand is no trifling matter for a motorcycle, and any kind of pound-for-pound, inch-for-inch, dollar-for-dollar comparison with big-bore Japanese motorcycles would leave a prospective owner double-checking his wallet pocket, and wondering whether BMW issues highwaymen's bandanas. When you measure miles ridden against money paid, things look a little different. You pay more, and, if our staff experience is any indicator, you ride more. And that's no bad deal.

Source Cycle 1982