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BMW R 100RT

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Make Model

BMW R 100RT Mono

Year

1990 - 94

Engine

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

Capacity

980 cc 59.8 cu in
Bore x Stroke 94 x 70.6 mm
Cooling System Air cooled
Compression Ratio 8.45:1
Lubrication Wet sump

Induction

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

Ignition 

Battery ignition
Alternator Bosch 12V/240 W
Battery Bosch 0.6 hp (from 1978: 0.7 Kw)
Starting Electric

Max Power

43.7 kW / 60 hp @ 7000 rpm

Max Torque

74 Nm / 7.5 kgf-m / 54.6 ft-lb @ 6000 rpm
Clutch Dry single plate, with diaphragm spring

Transmission 

5 Speed 
Gear Ratio 1st 4.4 / 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

Monolever swinging arm

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 1.85 B 19
Rear Wheel 2.75 C 18

Front Tyre

3.25 H-19

Rear Tyre

4.00 H-18
Dimensions

Length  2110 mm / 87 in

Width     746 mm / 29.37 in

Height   1465 mm / 57.67 in

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

Wet Weight

238 Kg / 525 lbs

Fuel Capacity 

24 Litres / 6.3 US gal

Consumption Average

5.1 L/100 km / 19.6 km/l / 46 US mpg

Standing ¼ Mile  

13.8 sec / 153 km/h / 95 mph

Top Speed

203 km/h / 126 mph
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In 1987sees BMW's resurrection of the 1000cc Boxer, in RT (touring), RS (sport-touring) and GS (Paris-Dakar dual-purpose) guises. They're not bikes that BMW intended to produce even a few years ago; the liter-size Boxer was to have been made obsolete in 1985 by the K100 flat-Fours. But BMW discovered that many of its loyal followers would never be won over by the K-bikes, and that they had no desire to replace their old 1000cc Twins with the only surviving Boxers, the smaller, less-powerful 800cc Twins. Instead, what they wanted was an improved big Boxer.

And in the R100RT tourer, that's exactly what BMW has given them. It's better than the same model of four years ago, itself a good motorcycle. At the same time, this newest RT retains many of the BMW quirks that drive some non-BMW riders batty. It's a machine for the faithful that might not entice many new riders into the BMW Twins camp.

If so, that's a shame, because in many ways the RT is a charmer, especially in its engine character. This latest " 1000" Boxer still displaces an actual 980cc, and still emphasizes a broad, smooth powerband. Actually, its low-end power has been increased this year through a slightly higher compression ratio than its 1984 predecessor, as well as smaller carburetors and an exhaust system tuned for torque. The engine pulls hard from just ofTidle and feels particularly strong in the 3000-to-5000-rpm range before fading slightly near its 7000-rpm redline. It gives little hint that it makes only 60 peak horsepower; in this 500-pound tourer, the Twin provides good power for accelerating and cruising at any speed up to an indicated 90 mph, and will push the barn-door fairing through the air as fast as 105 mph. Only in its cold-bloodedness after starting is this engine in any way less than satisfying.

For instance, one complaint about former versions of the big Boxer—vibration—seems less called-for on this model. Oh, the new engine quakes and shakes a bit, and the individual power pulses hammer the driveline if you apply full throttle at 2000 rpm or so in top gear; but that low-frequency throbbing is less annoying than the buzzing of some more-modern Fours, including the K100. Rather, it's a more lulling pulse that simply tells you that all is alive and well in the engine compartment.

The chassis that carries the Boxer motor is basically the same Monolever (BMW's name for its single-sided swing-arm) design that was used on last year's R80RT. Particularly noteworthy are the 38.5mm-diameter fork tubes, 25mm front axle and rugged fork brace that all make for a very stiff fork assembly and precise steering. Suspension, though, is classic BMW: soft and very lightly damped. The RT doesn't have the precise, controlled suspension of a BMW automobile; it instead has the pillowy float of a Cadillac. That makes rider smoothness critical on the RT, for any jerkiness by the operator is amplified into exaggerated pitching of the chassis on its soft suspension.

Not that the RT can't be ridden quickly on a twisty road; it can. But it demands the riding techniques used by veteran BMW riders: very little braking (they use the engine instead), wide and smooth lines, and constant or smoothly rising throttle through corners. This riding style minimizes fork dive and shaft-drive-induced pitching, but BMW should really fix the source of the problem. More-sophisticated fork springing and damping would help, but the best solution would be to adapt the new Paralever rear suspension (as used on the '88 R100GS) to the RT.

Other aspects of this touring bike are more pleasing. The fairing gives exceptional weather-protection, though the windshield needs to be taller for riders over 5 feet 10. The riding postion is very good, spacious with well-placed handgrips, and even the ankle-to-carburetor clearance has been increased slightly so that bruised shins are no longer a requirement for RT riders. The luggage, from the K100, is easy to mount and dismount, and no longer rattles on its frames as did the luggage on the previous R100RT.

But a few quirks remain. The RT's seat is still flat and fairly hard; and though it's not uncomfortable, it's not inviting, either. The RT's fork lock is hidden away on the steering head, where it is very difficult to use on a dark night. And the spring-loaded sidestand simply seems a cruel and treacherous joke.

Still, the R100RT is an interesting motorcycle, a lightweight, comfortable and simple touring bike, the very antithesis of the Japanese heavyweight luxury cruiser. Longtime BMW riders will love it. But while everyone else might share some of that enthusiasm, a few improvements to suspension, seat and hardware would make the RT easier for all to love.

Source Cycle World 1988