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BMW R 100RS

 

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Make Model

BMW R 100RS

Year

1976

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

Road Test

Cycle World 1976
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How do you put a price on prestige and quality? If someone built a pushrod, twin-cylinder motor cycle with an engine whose basic design was decades old, and marketed it at a price many hundreds of pounds higher than its rivals, would it sell? All logic says that it shouldn't, but that is exactly what the BMW motor cycle company does for a living and a very good living it makes too.  BMW's secret is that its bikes have proved their quality and dependability over the years. In absolute terms, the company doesn't make a great many bikes and their exclusivity, quality and high price has given BMW the kind of image that is usually associated with Rolls-Royce, caviar and the executive jet set.

Top of BMW's range is the R100RS model, the most remarkable feature of which is a sleek fairing designed to make high-speed touring a comfortable and practical proposition, rather than to improve outright top speed. The R100RS was a logical progression for BMW because its products were best known for their long distance cruising ability and the RS was simply an attempt to create the ultimate sports tourer, whereas the R100S, with its very small fairing was the more normal sports bike.  The R100RS is powered by a horizontally opposed, twin cylinder engine of 980cc which, fitted with two 40 mm Bing carburettors, develops 70bhp at 7250 rpm (5 bhp more than the S). This gives the bike a top speed of around 125 mph, hampered as it is by the large fairing; but then high speed blasting is not what BMW's are all about.  When the weather turns nasty the R100RS comes into its own. The fairing designed in the Pininfarina wind tunnel in Italy is so effective that wind and rain are deflected around the rider enabling him to travel in comfort and arrive clean and dry.  Riding the R100RS is an interesting experience.

There is a slight boom from the fairing, but the engine is uncannily quiet and smooth. The fairing is so well designed and engineered that wind noise is minimal and it isn't until the rider looks at the speedometer that he realizes he is doing 20 mph more than he thought he was. In addition, the handling and braking of the big BMW are superb and even the trickiest of bends can be taken with surefooted confidence. Some riders worry about grounding the cylinder heads, exposed as they are on the sides of the machine, but this fear is unfounded. Even the most spectacular road racer would be hard pressed to get the smart black cylinder heads anywhere near the road.

 Apart from its impressive ride, the BMW's other major asset is its excellent fuel consumption. With a 5-1/4-gallon tank and an overall fuel consumption of 50mpg, the BMW has a first-class range, a feature so important to the hardened tourer.  Another impressive aspect of the R100RS is its marvelous finish. Unlike its Japanese rivals, BMW does not launch new bikes every two weeks, but tends to stick to a small handful of models which are constantly being refined. Consequently the detailed finish of the BMW is immaculate and at the same time practical.  A quality image is not something that can be achieved overnight; it takes patience, time and a great deal of work. BMWs are more expensive than most of their rivals, but few of their owners would disagree that sometimes it just isn't possible to put a price on real class.

Source Super Bikes by Mike Winfield

Motorcycle list magazine review 1977

IF you are expecting a list of superlatives to describe the new BMW R100RS as the most mouth-watering motorcycle ever, then stand by for a surprise because I have to reveal that this £2,899 wunderbike is an •annoying machine on several counts. First, the Bee Emm's 100 mph cruising speed turns the "temporary" speed limitations into a pathetic pedestrian plod, particularly frustrating when the law is making a concerted effort to take away your driving licence. Second, the sheer luxury of being able to ride fast and hard in utter confidence has spoilt me for any other bike I ride. Third, even if I mortgage the wife and kids, I'll never be able to afford one, Goddammit.

Alright, so it's slipped out — I like it, but I make no apologies for joining the BMW - is -best bandwagon. Anyone who rides a lot of motorcycles over a lot of miles wants a machine to handle, steer and stop as rapidly and precisely as the will that commands it, plus a top speed way in excess of anything they are likely to use so there is effortless power at the flick of a wrist. Next to that comes a degree of comfort that permits a day-long ride of 600 miles without the rider collapsing in a state of exhaustion.

The BMW is not perfect in fact there are quite a few minor things wrong with it — but in all the major requirements of a very serious motorcycle for a very serious (and wealthv) motorcyclist the R100RS is outstanding.From the moment you get your leg over the streamlined hump of the single - cum -dual seat, lean forward to grasp the short and low handlebars, and find that your feet drop onto the footrests without having to look where to find them, you know the bike feels right. Certainly any apprehension about riding such a big and expensive machine vanishes as soon as the motor is started when, with a single stab of the starter button the 980cc flat twin shakes itself into life and throbs away.

Selecting first gear, which came with a firm click after two prods on the pedal, reminded me that BMW's gearchange is their renowned Achilles heel, and I made a mental note to see whether the cogbox on this unashamedly upper-class motorcycle was anything to be snobbish about, or as embarrassingly clonky as other BMs. It did seem better than the R90S, but it still emits a solid "thunk" with each gear if you are careless in gear-changing. After a while I found that by co-ordinating the movement of throttle, clutch and gear lever the ratios would slip in and out quickly and silently. Nevertheless, I have every sympathy with the guy who has just paid the best part of £3,000 for a motorcycle, and finds the transmission anything less than perfect. One change I could never execute silently and swiftly was between first and second gear, but apart from accidentally hitting neutral a couple of times I never missed a change, and consider the gearbox something that can be lived with.

The ratios were otherwise very well chosen, and with a wide spread of muscle that took the machine from a shuddering surge at 2,000 rpm up to a bass howl at 7,000 rpm, there was little need for gearchanging. I frequently used top as an "automatic" when I wanted to travel smoothly and quickly with minimum effort, and only used the maximum revs and power when I wanted to clear away the office cobwebs with the floo of adrenalin. Then, the bike's performance was not far short of mind-blowing, in a deceptive sort of way.

It wasn't the arm-wrenching acceleration of a 900 Kawasaki, or the frenetic wheelie-popping surge of some of the quick two strokes, but at every bend, or every time I checked the speedo, I found I was travelling much faster than I thought. On our acceleration tests, the BM clocked 13.5 sees for the standing quarter mile, despite the rear wheel spinning wildly on the damp track. Surprisingly, the R100RS produces less bhp than its predecessor the R90S, but has such a boost in torque that a rider is unlikely to notice the fractional reduction in top-end go. In fact, the fairing probably cancels out the two bhp loss in power.

Sticking to the 50 mph speed limit, the BMW woofles along at 2,750 rpm in top yet will react instantly to the throttle to give instant overtaking ability. Even at 85 mph the motor is only spinning at 5,000 rpm, and never feels to be exerting itself. From 30 mph to well over 100, the fat spread of torque provides top gear, performance that many other big bikes can't even begin to match.

The BMW motor's long-legged gait, and superlative suspension and handling obviously played a part in the machine's effortless progress on the road, but most of the credit must go to the fairing. Unlike the usual conglomeration of fibreglass bits and bulky brackets, usually tacked on as a "fits-mostbigbikes" extra, this injection moulded ABS bodywork looks and feels like an integral part of the motorcycle.

It's easy to believe BMW's claim that the fairing was intensively wind-tunnel tested to find the best aerodynamic shape considering the luxurious comfort it affords. With the fairing you can cruise the R100RS at 100 mph plus all day without the strain of being buffeted by a hurricane, and the wing shapes incorporated into it's design helps high speed stability by putting more weight on the front wheel.

There are a couple of complaints though — the fairing so effectively reduces wind pressure that the rider's full weight goes onto the bars, and at first I suffered wrist ache. Another debit point is that the slipstream produced a draught from behind, which whistled up the back of my helmet and down the collar of my riding suit. The screen is low enough to see over in all but a chin - on - the - tank crouch, which is just as well as the plastic distorts vision considerably. All in all, the fairing represents real progress in motorcycle manufacturer's thinking, and it can only be hoped that BMW's example starts a new trend in the manufacture of fully equipped road going bikes, whatever their size.

For a near £3,000 motorbike the BMW has quite a few detail disappointments: like the screen edge trim which peeled off during the test, and the headlamp window in the fairing which leaked, allowing dirt contaminated water to dirty the inside of the glass where it reduced headlamp power, and was impossible to clean. The steering damper, too, could have done with much clearer markings to make it easier to see what the setting was while riding. The edges of the seat pan were so thinly covered with sponge that they dug into the thighs when stopped at traffic lights etc.

The seat was poor in other respects, too. It is big enough for one -and - a - half people making it almost as unsuitable for solo use as with a pillion passenger crammed in behind. The hump is too far back for anyone but a giant to use it as support, yet far enough forward to force the rider to sit on the back of the tank with his knees outside the fairing whenever he takes a passenger. It is amazing that this seat should be a product of Germany, where it has not got design approval for carrying a passenger, and RIOORS's fitted with it cannot be sold with pillion footrests over there. The natty cutaway hand-holds in the seat for the pillion rider are small consolation, but shorties like me will be pleased to know that it is easy to get both feet comfortably on the ground, thanks to the low seat. The bike is available with a proper dual seat but it must be ordered specially.

The advantages of developing and improving a long established design are evident in the 100RS's handling, steering and suspension, which seem almost unimprovable. The long-travel forks and rear suspension are sprung and damped to near perfection, and most bumps are absorbed with no shock getting through to the rider, although it is still possible to feel exactly what the wheels are doing.

Steering is light and easy at low speeds and the Metzeler tyres are superb, even in the wet. There is no wallowing, weaving or yawing, or any other handling vices that tend to spoil so many big capacity motorcycles and yet you can guide the machine with no more than a light pull on the bars and knee pressure on the five gallon petrol tank. Talking about the tank, it gives a range of well over 200 miles with fuel consumption between the mid forties and low fifties. Over the test, which included track performance and relatively sedate touring, the BM returned an average of 47 mpg, the best being 54 mpg, and worst 42 mpg, which is good for a big, high performance sportster.

The tank cap on the latest range of BMs is a hefty screw-in device, looking rather like a large Thermos.flask stopper, with a lock and flap-up handle incorporated in the design which makes it virtually leak-proof in a spill (sic). The whole lot lies flush with the tank top to meet US legislation.

The brakes, or rather the twin drilled disc set up at the front was disappointing. It lacked positive bite and needed quite a lot of pressure to haul the bike down from high speeds in a hurry. It wasn't dangerous, but only just adequate. Operation in the wet, however, was very safe, thanks to the perforated discs which could be heard buzzing during low speed braking. The rear drum brake was very good with plenty of feel and a January 1977 positive action when used in anger. On the brighter side, the quartz halogen headlamp was really good. Despite having to get through an extra layer of glass in the fairing, the beam bathed the road and verges with light and allowed rapid night time travel in safety. The dip switch cut the beam dead before it dazzled other drivers, but gives a slice of light up the nearside verge, where it's wanted.

Switchgear took a little getting used to, particularly the down - for - right, up - for -left winker switch on the twistgrip console. The matching dipper mechanism on the other bar is cleverly designed to incorporate the headlamp flasher with the horn button in easy thumb-reach above it.

The twin tone horns let out enough noise to wake a sleeping policeman (who the hell wants to do that? Ed.) and are just the thing for warning motorists at "T" junctions that you are using the road as well as them.

A cockpit full of instruments saves anybody being lulled to sleep by the soothing mumble of engine and rock of suspension while cruising the highway, by providing enough information to keep the brain actively engaged computing distance travelled against time elapsed compared to cruising speed etc. Onecynic said: "Wot, don't it tell yer when yer going to arrive then. Huh, loada rubbish" and rode away smugly on his Triumph.

But with the exception of the battery condition indicator, all the equipment is worthwhile. Particularly pleasing are the mirrors mounted on the fairing which give an excellent view behind. Finish was what you would expect of a vehicle with the BMW name on it and, apart from a small oversight which lets water into the tool compartment, every part of the machine has been carefully thought out. There was a good quality, comprehensive tool-kit, and hand pump for the tyres.

That still leaves us with the question: is it worth £2,900 when you can get a 900 Kawasaki for half that? Certainly the Z900 represents remarkable value for money, but if you are a biking devotee and can scrape up the bread, the BMW R100RS is worth every penny.