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BMW K100RT Road Test

Jan 1985

I can already hear the disembodied moans of some of our accredited 476,000 readers. "What yet another K100RT test? Didn't we have one just two months back with much huffing and puffing about BMW's legendary press launch hospitality backed by a few tub-thumping observations of the actual motorised bicycle?

Well yes, we did but you see that was about vo sunny days and 300 miles over Corsican lountains and this one's about two weeks and 200 miles around blowy Blighty in early-closing, te October. Moreover, it tries to assess the 1500 difference between the RT and say, a 1000 Ninja or FJ and questions why the ideniably expensive K100 series is a class best seller all over Europe and particularly in the UK.

Well, I don't. I thought nobody had any money any more and BMWs were largely dreambikes of the undercapitalised buying public. And turally that is still very much the case even jugh BMW GB are selling more bikes in the 900 1300cc division than anybody else. At the end October they held a 35 per cent share of the jerbike league which made them easy market ders well in front of the likes of Kawasaki (21 per cent) and Yamaha.

Two weeks in the UK taught me a lot about the RT and still something more about high-speed, high-quality motorcycling. Unlike both RTs I'd ridden in Corsica, this one didn't display tingling vibration that seizes up your throttle hand nor did it make much in the way of unprompted noises from the fuel tank and injectors. Hence two of my main snivelling criticisms could no longer be levelled. Our fleet RT had 3500 miles up and was a definite good 'un. Naturally it had a few peculiarities of its own like some wayward instrumentation electronics and a dodgy pannier, but these are fixable unlike even mildly unacceptable engine vibration. This one was a peach and a consummate pleasure to drive.

Certainly, I've never covered long, 500 mile days in such untiring comfort. In a straight line, its tested top speed was 132mph against a slight headwind but displaying no buffetting, no weaving, no problems, nothing but a rigid adherence to a straight and stable line. More often on a high-speed road like the A1 you'd be sitting relaxed and untroubled at 110mph, effortlessly banking through the long dual-carriageway curves even on a wet road. It is a remarkably confident and inspiring motorcycle.

At speeds over 100mph it just doesn't feel that fast because you're sitting pretty and feeling laid-back. There's just nothing to detract from your riding enjoyment. One day I played tag with a well-driven Porsche along the A5 and onto the motorway and could stretch ahead into the distance for as long as my police paranoia allowed. I like to think we shared a similar view of the road — fast, carefree and shielded from the elements. I had acceleration and nimbleness. He probably had more leg room and could smoke. Even allowing for time lost by rny insatiable tobacco craving (I have to quit every 120 miles for a draw) I was still averaging 75mph over A-roads. This bike gets you from A to B on the map quicker and more civilised than any other bike I've ever ridden. Others offer bigger balls but less protection, some have sharper, sportier handling but require more effort and have less grace. The RT is a complete road tool package. It's only when you can despatch the distance at over 100mph in such calm, rarefied comfort that you know you're really travelling, first-class.

At first I thought the wind rush at high speed was being directed clean over the top of my helmet, not so, ride with your visor even slightly open at 100mph and it rattles. For a six-footer, the airstream is actually hitting you square in the face though its force is so expertly broken up and dissipated by that top lip spoiler you don't notice it. The fairing was good in the rain too. In gentle drizzle around town you can ride in jeans and never get particularly wet. In a downpour at speed, the fairing excellently deflects the water around and away from the rider. Even the mirrors work aerodynamically keeping the wind off your hands. Their much-publicised break-off facility proved useful too, like when I snapped one off wheeling the bike around Motad's dyno room.

The RT is a beautiful bike to drive fast. With 80 per cent of its maximum torque available at only 3400rpm, it's a tourer's dream, slot it into top and just roll it on. At 100mph the motor's spinning at a leisurely 6500rpm. The power delivery throughout is smooth, vibration free (at least on this particular model) offering wonderful traction and performance. Though it has considerable poke it never even threatens to unload the tyres, it just drives, perfectly balanced and responsive. The dyno revealed a fairly smooth curve with one noticeable hump, between 5200 and 5600rpm where it makes over 10hp in one big gulp, though you don't notice this on the road. Out on the black stuff it's just all roll-on power with plenty of acceleration and urgency through the gears, enough to match all but the biggest Jap roadburners which will realistically pull away up to a crucial point above 100mph where the RT's superb aerodynamics come into their own and will effortlessly restore the horsepower difference. Sensible and safe, exciting and extremely efficient — these are the performance paradigms BMW have always worked within — and the RT is quite simply the best yet. The best touring motorcycle in the world, no question.

Idling gently on its centrestand, it would seem you can definitely beat the fuel injection system with your hand. Crack it open and it lags a bit behind, you can't kill it but you can beat it. Again, this anomaly doesn't really translate to on-the-road performance. The only lag in response I could discover while riding was if you shut off and then opened up again very quickly, when there's a slight delay probably attributable to the trick fuel cut-off facility (the Bosch LE Jetronic system stops the gas flow when the throttle is shut refusing to reinstate it until you open the throttle again or engine speed falls below 2000rpm). Generally, the injection system is excellent, effecting a tricky technological compromise between sharpness, economy and reliability. Gas returns averaged 43mpg over two weeks of pretty hard use. The lowest 4.84gal tankful return was 39.3mpg over 132 miles of scorching performance. Our best figure was only 45.7mpg but we weren't trying and I don't doubt BMW's quoted consumption averages of 64 and 48mpg at a constant 55 and 75mph. Not bad for a full one litre motorcycle.

Less impressive are the petrol warning lights — the yellow 7 litres tell-tale flickers well before 100 miles are logged and is on continually once over the accumulated ton. The red 4 litre light induces petrol panic, it's always on by 130 and by 140 you've got sick of it, so stop and fill up only to find you've still got 5 litres left sloshing around.

The gas tank has a theoretical range of at least 170 miles and possibly over 200. The warning lights have a dismal range of accuracy (they're about 100 per cent wrong most of the time) and if BMW can't improve them then they should reinstate that low-tech device that never lies — the humble reserve tap.

Perversely, the instrumentation is one of the RT's weakest points. The faulty fuel lights are top of the list, the electronic speedo, tach and clock are accurate and useful, the choke and rear light tell-tale are largely superfluous, while the digital gear indicator might conceivably be of interest except ours didn't work. It read 5 in first, 4 in neutral and nothing at all in the top three gears. Tapping the glass had no effect. Whacking the whole pod with a fist brought a flickering green neutral light and a semblance of seriousness. Ah ha, a loose connection. But just you try and get to it. You can no longer reach the back of the instrument pod from round the front and up where the fork legs go because they've efficiently sealed off that whole area. Nor can you reach the rear of the clocks without dropping the fairing and all for the sake of one multi-pin connector. Actually the whole of the rubber mounted instrument binnacle does bounce around rather a lot, seemingly soaking up the hammering of the fork action, though it doesn't affect the main instruments accuracy or legibility.

On the rolling road dyno our test bike made 84.4 rear wheel horsepower at 8500rpm. Compare that to a laimed maximum of 90bhp at SOOOrpm and you'll see why BMW have been rightly trumpeting the merits of their Compact Drive System and transmission. From the crank the drive is geared directly to an input shaft then via the single plate clutch to a hollow gearbox shaft and thence to the five speed, three shaft gearbox. There are dampers everywhere along the driveline to smooth out load changes and eliminate vibration. The result is clean and unobtrusive shaft drive. The back end still rises and falls a bit on and off the gas but it's nowhere near as marked as on the old boxer twins. The gearbox is not as slick on clutchless changes as our GS80 but is infinitely better in action than the clunky, often hit and miss, 1000cc boxers.

Details of the K100 engine have been well documented this year and since all three models share the same powerplant and running gear, I'll just repeat my earlier opinion of the engine which is that with a sub-four second, 0-60mph capability, a generous, useable spread of torque and power and a top end of over 130mph. which is wholly realistic and attainable, the motor is pretty much faultless, a really useable and versatile unit. Civilised, comfortable, quick and strong. What more could you want?

The RT's handling was much as experienced in the arduous mountains of Corsica. It's redoubtably stable at all speeds, steers comfortably, brakes sharply and genuinely assists the rider instead of fighting against his input demands. One or two observations. The front end displays some resistance and vagueness in slow turns, it doesn't drop in smartly or sweetly, the wheel just doesn't want to deviate from its straight ahead path. Why this should be I don't know since it's fine at speed. As it is you just have to force it by turning the rubber-mounted and high handlebars more. Snap it in quick.

It doesn't dive dramatically on the brakes despite offering 7.Sin of luxurious travel and no pre-load or damping adjustment. Actually the progressive spring rates have been carefully calculated and the telehydraulic 41.4mm stanchions contain double-acting hydraulic dampers. There's no gimmicky anti-dive (hardly surprising) and no fork brace. BMW's engineers had at least looked at the latter possibility but had rejected all current fork braces as being "technically inadequate". Doubtless some kind of brace will appear on big BMWs in the future though their R and D team are notoriously reluctant to adopt anything until it's been exhaustively tried, tested, proven and digested. (I mean, they were five years behind everyone else in adopting tubeless tyres as OE. Whatever next — the four valve head?).

The rear single Monolever swing arm and shock is a fine combination. The arm is made of strong yet light alloy supported on the gearbox by taper rollers. The monoshock spring has a gas filled damper and three pre-load settings for the progressive rate spring. Position one was good for cushioning the bumps but a bit washy on fast lines over the smooth stuff, position two was much better even with a passenger.

Pillion riders all bemoaned the lack of a proper grab rail. The integral seat hand-holds are just not deep enough for gloved fingers to get a decent grip on, also it's a bit of an unnatural position. No such complaints about the seat. Sure the rider gets traces of numb-arse after about three hours in the saddle but whatdayaexpect? Even a big, six foot rider can get his knees tucked in comfortably behind the fairing lowers though when you want to put a foot down your knee disconcertingly brushes the said lower. It's not hard to imagine that one dreaded time when, encased maybe' in leathers and an oversuit, you go to put a foot down, your knee gets momentarily stuck and you fall over in a big heap. It didn't happen to me but I know it's happened to others.

The brakes are ace. I still don't like the way the bike stands up if you brake while lent over but in normal use the three 11.2in slotted discs, fixed calipers and semi-metallic pads are a strong and trustworthy set-up. The ront pair squealed throughout. The rear (a very interesting arrangement, partially inboard of the drive system has a lovely long and lazy action with all the feel of a drum but ultimately the bite of a decent, progressive disc. With carefully calculated lever pressures all round you'd have to be very stupid tc fall off the RT under locked anchors.

Night riding proved no problem. Both the dipped and main beam of the big H4 55/60W headlight are a joy to ride with, slicing the darkness and allowing road speed averages only slightly lower than during daytime riding. On one long trip I was contentedly covering the last 100 miles to London at night reflecting smugly on how nothing had come past me all day, when a rider did come past, fairly fast and a bit ragged. He was a German on a K100RS and had the appearance of someone desperately lost and running out of time. I hung on for a while but couldn't be bothered to chase him all the way into town. Strange to note though that what looked like ragged riding was actually well within the control of the rider. The K series, like the boxers before them, have considerable ability to forgive rider errors and just let you get on with the job.

The 12V 20 amp/hour battery wouldn't turn over a friend's wanked-out car battery. It's a bugger to get at as well, off with the side panels and the seat, partially dislodge a tray which splits but is not easily removable since a bulky combination of fuel tank and injector sensor wiring runs through it, flip up the battery terminal covers connect and . . . nothing. It started first time jumped from another venerable old cage. A BMW 30A/h battery is available as an optional extra, though the standard one never gave any problems in actually running the bike. It always started first.