If you fancy yourself a high-stakes gambler, consider what BMW has just done:
wager 60 years of success with opposed-Twin motorcycles on the K100, an entirely
new inline-Four. Now back that bet with a $110 million investment in
development, tooling and the construction of a new factory as BMW just has, and
the wager takes on proportions that are too rich for even a fat-cat Las Vegas
gambler to handle.
There are those who will argue, and rightfully so, that BMW had to do
something, that even though Max Friz's 60-year-old Boxer motor was most
certainly a Good Thing, all good things must come to an end sometime. And for
Good.
Thing, that sometime was not far off. The Twin already was laboring to pump
out a meager 70 horsepower in its one-liter form, and upcoming noise and
pollution regulations would have made maintaining even the present levels of
performance more difficult than squeezing blood from a rock.
BMW, more than anyone, had seen the handwriting on the wall, so it stopped
building the R100 models altogether, and has drastically cut the number of 650cc
and 800cc Twins that will roll off the production line in the near future. The
company's brand-new manufacturing facility in Berlin will produce 33,000
motorcycles this year an increase of 20 percent over last year—22,000 of which
will be K100 models: the standard, unfaired K100 ($5990), the sporty K100RS you
see here ($7200), and the touring K100RT ($7500), all of which share the same
basic engine and chassis.
What's even more chancy about BMW's gamble is that the company is playing a
hand it dealt itself almost six years ago, back when the decision was first made
to build the K100. At that time, the technocrats at BMW were charged with
building a machine that would not only meet the projected performance criteria
of the Eighties, but one that would offer traditional BMW values— longevity,
luxury, serviceability and, perhaps most important of all, exclusivity in a
market soon to be inundated with exotica from Japan.
Simply put, the Germans needed to build a machine that the Japanese would
not. And in the quest for such individuality, many engine configurations were
either tried or at least considered. V-types, square-Fours, far-fetched
H-designs, even a horizontally opposed flat-Four was evaluated, although it was
abandoned once it was deemed too similar to Honda's Gold Wing. Eventually, the
decision was made to build a new machine powered by a dohc, liquid-cooled, fuel
injected, one-liter inline-Four laid on its side with its crankshaft running
longitudinally. And after making that commitment, the powers-that-be at BMW must
have gnawed their fingernails to the quick as new engine designs from Japan
started bombarding the marketplace all around them.
Luckily for BMW, there were no direct hits. And finally, after five years of
development that included 10,000 hours of dyno time and 400,000 kilometers of
test riding, the K100 became a production reality for the European market late
last year. Now it's America's turn. And those who have feared that the precious
essence of BMW would somehow be boiled away by the brewing of this new formula
need worry no more. Because the most endearing of BMW qualities are
present—indeed, maybe even enhanced in the K100.
Now, understand that even though the K100RS tested here looks nothing at all
like a Japanese bike and even less like its predecessor, the R100RS, it has been
heavily influenced by both. The lazy lope and subdued rumble of the flat-Twin
engine have been replaced with a more urgent, higher-frequency whine, the same
kind of four-cylinder song sung by the inline-Fours from the Orient; yet the
bike still has the same air of dignity that marked the R100RS. It gobbles up
highway miles in grand BMW style, but also can be snapped into and out of
corners with a precision and surefootedness that no Boxer could ever match. It's
a bike that can be herded along a twisty ribbon of road in the company of the
best high-performance Japanese iron without losing its stately composure. So in
effect, it's the best of both worlds.
There's no question that a really fast rider on a really competent Japanese
sportbike can get from Point A to Point B on a winding road much faster than he
could on a K100RS; but most everyone else can ride just as fast, if not
faster, on the BMW while not working as hard in the process. The K100 has
the kind of powerband, the kind of suspension and the kind of overall handling
that simply make the fine art of riding quickly a whole lot easier.
There is no mystery about how the K100RS accomplishes this feat; BMW merely
rethought and rearranged existing technology to fit within some new parameters.
In fact, poking around in the RS's twin-cam, 987cc engine reveals anything
but cutting-edge hardware. The bore-and-stroke dimensions are un-fashionably
undersquare (67mm by 70mm, respectively), the cylinder head is of a bog-standard
two-valve design, and valve adjustment is via the same type of shim-and-bucket
arrangement that has been bumping poppet valves open for decades. Only the
narrow, 38-degree included valve angle is in keeping with current trends in
engine design.
But there's a good reason for all of the K100's apparent low-tech: It fits
the requirements imposed by the use of a longitudinal, inline-four engine of
one-liter capacity. Were the cylinders any larger in diameter, the engine would
have to be longer, for the bores already are marginally close together (9mm);
and a longer engine would, in turn, mandate either a lengthier wheelbase (which
is already quite long) or a shorter swingarm (which, if it were much shorter,
would excessively amplify the up-and-down chassis-jacking caused by the shaft
drive's torque-reaction). And since that more-or-less locked BMW into a smallbore, long-stroke engine (which is not conducive to high-rpm operation), a
four-valve combustion chamber (which reaps its biggest benefits at higher rpm)
made little sense.
On the other hand, the shim-and-bucket valve gear made perfect sense
in the K100 engine. Not only does that arrangement meet BMW's requirements for
simplicity and long intervals between adjustments, but it allows the camshafts
and followers to be easily serviceable just by removing the cam cover on the
left side of the motor. So, too, are the K-model's forged, one-piece crankshaft
and its attendant plain bearings highly accessible, for they're all located just
beneath the easy-to-remove aluminum cover at the right side of the engine.
Like late-model Boxer Twins, the K100 Four uses an electronically applied,
nickel/silicon-carbide coating (called "Scanimet") on its aluminum cylinder
bores, which are cast as a unit with the upper, left-side engine case. Aside
from being non-boreable, this coated surface is superior to a cast-iron liner in
terms of thermal conductivity, plus it allows for closer bore-centers, and is
lighter and more durable. Durability also was the prime reason for the use of
liquid-cooling on the K100. And the fact that previous BMW motorcycles have been
air-cooled was no drawback; the company has, after all, been building
liquid-cooled BMW automobiles for a long, long time.
BMW's expertise with automobiles also was put to good use in the adaption of
fuel injection to the K100. The bike incorporates a variation of the Bosch LE-Jetronic
system used on numerous BMW cars for years. This system utilizes a black-box
computer (under the RS's seat) that, through a series of sensors positioned in
key locations in and around the engine, keeps tabs on engine speed and
temperature, throttle position, and the air temperature and pressure within the
intake tract. That information is analyzed by the computer, which then regulates
accordingly the flow of fuel through the injector nozzle situated in each intake
port. But that's all pretty much standard fare for a fuel-injected motorcycle,
with one exception: On the K100, a Bosch-built electronic fuel pump is housed
inside of the bike's 5.8-gallon aluminum tank as a part of a unique,
completely sealed fuel system.
Bosch also supplied the K100's electronic ignition, which is tied into the
injection system's computer box so it functions as both a performance aid and a
rev-limiter. By comparing engine rpm with the amount of throttle opening, the
ignition effectively selects one of two distinct advance curves to work most
effectively with the load that's being placed on the engine. In addition, at
8650 rpm, which is just 100 rpm above redline, the ignition automatically
retards the timing to deter over-revving. And should the rider ignore that first
warning, the computer then shuts off the fuel-injection system altogether at
8750 rpm, and keeps it off until the engine speed drops back down to below 8750
rpm.
That fail-safe capacity is about the most sophisticated aspect of the
K100's
engine. But otherwise, the bike has an unremarkable, long-stroke, two-valve,
relatively low-revving motor that fits right in with the performance program
outlined by BMW's engineers right from the beginning: strong torque output at
exceptionally low rpm, and a healthy if not spectacular peak horsepower
production at only moderately high rpm. That's just what the K100RS has, too.
The torque peak is at 6000 rpm, but the engine achieves 85 percent of that peak
at 3500 rpm; and the claimed 90 horsepower is delivered at 8000 rpm, still well
below the power peak for virtually all comparable Japanese engines.
What those numbers mean is that even though the K100RS isn't going to win any
contests of speed with Japanese weaponry of equal displacement, the bike still
is no slouch. Actually, it's faster than, say, a Suzuki GS850 shafty in just
about every conceivable way, from an idling crawl to triple-digit speeds and
everywhere in between. Arid it does that by producing the kind of
power that is generally found only on something like a Honda Interceptor—smooth,
uninterrupted, linear.
So no matter the situation, whether it's cruising the open highway or
clipping along some remote country backroad at a classic sport-touring pace, the
BMW always seems to offer you two, maybe three usable gears to choose from. And
although the K100RS admittedly is no FJ1100-killing roadburner, it still romped
through the quarter-mile in 12.56 seconds and 107.20 mph—not bad, considering
that the RS has rather tall gearing, taller, even, than the standard K100's.
There's also an uncanny smoothness in the way the K100 reacts to changes in
throttle. Off of idle in neutral, the engine seems to respond slowly, almost
with a stumble. But when the bike is in gear and moving along, it offers a
nearly perfect compromise between immediate response and gradual reaction.
There's virtually no driveline snatch, no sudden lurches, no tendency to fall on
its face, just a turbine-like outpouring of strong, steady power.
There is, however, a glitch or two in the K-bike's performance program, not
the least of which is what seems like a rather fragile clutch. Indeed, in the
middle of only the third run down the dragstrip, the single-plate dry clutch in
our K100RS fried itself to a crisp. Then there's the matter of the vibration
radiated by this new-wave BMW. Despite being rubber-mounted in the front, the
engine buzzes noticeably more than a Japanese inline-Four of comparable size,
and certainly more than any Boxer Twin ever managed on its worst day. It's a
fairly high-frequency vibration, too, that is strongest right at about 55 mph in
top gear, and it's felt most often through the footpegs. And the vibes didn't go
unnoticed by the heat shield on the muffler, which self-destructed its front
mounting
So that improvement, along with the use of three low-lash cushion mechanisms
in the driveline (one spring-type cushion and two hard-rubber types) in place of
the the two in the Boxer (both of the coil-spring variety), has eliminated most
of the driveline free play that made riding the old bike smoothly such a chore.
Gear changing on the K-bikes is therefore not the least bit clunky or noisy, and
off-on-off throttle transitions are not greeted with the lurching made infamous
by the RI00 models.
Better yet, the K100 exhibits less of the up-and-down chassis-jacking that is
always a concern on shaft-driven bikes. Some of that is due to the fact that the
bike has slightly shorter suspension travel than the Boxer has, some is due to
the fact that the rear suspension has stiffer spring rates with more preload and
thus will not let the bike move up and down as dramatically. There still is a
pronounced rise and fall, especially in the lower gears, but the problem is less
exaggerated than it is on the R100 series.
Consequently, low-speed cornering in particular requires a bit of
throttle-control to prevent excessive vertical chassis movement. But unlike the
opposed-Twin BMWs, which often hammered their undercarriages into the road
surface when the suspension compressed quickly, the K100RS has an abundance of
cornering clearance in any case. The bike must be ridden extremely hard before first the footpegs, then the sidestand tang and the centerstand,
graze the pavement. And even when something solid does smack the macadam, the RS
remains unflinchingly stable.
One reason why the bike displays such good road manners is its use of fairly
sticky Metzeler Perfect tires, an 18-inch up front and a fat, 17-incher in the
rear. Another is the rigidity of the front fork, a Fichtel&Sachs-built assembly
using 41.4mm stanchion tubes held in place by thick aluminum triple-clamps. The
fork also features a front axle that has a huge, 22mm diameter to maximize the
rigidity of the entire assembly, and the axle also is offset 2.5mm to the rear
to increase the trail a like amount.
That sturdy fork is equipped with two very powerful Brembo brake calipers
pinching slotted, stainless-steel discs that are 285mm in diameter. The brake
pads are semi-metallic and provide consistent, effective stopping ability in
both wet and dry conditions. But although the front brake is powerful and
requires only two-fingered actuation to slow the RS at moderate speed, it calls
for a fistful of digits around the lever during high-speed braking. Despite its
high-effort action, though, the front brake does not fade, even when used
aggressively for long periods of time.
Not so the rear brake, which can be overheated with exceptionally hard use,
sometimes badly enough to stop working altogether. And when used in combination
with engine braking from fairly high rpm, the brake can also initiate some mild
rear-wheel chatter, which is aided by the soft rates of springing and damping in
the rear suspension.
BMW has always used long, soft suspension on its motorcycles, it seems; and
although the K100RS has a tad less travel at both ends than the Boxer models of
recent years, it is nonetheless plush, compliant and responsive to bumps of all
sizes. The fork action is above reproach in just about every respect, with the
possible exception of the dive it exhibits during severe braking. The fork
offers no external adjustments, but the single rear shock has a ramp-type collar
that allows the spring preload to be set at any one of three positions. At its
lowest setting, the rear end is pleasantly supple on the highway, but compresses
and moves around too much during aggressive cornering. At its highest setting,
the shock is best-suited for hauling a passenger and a few days' worth of
luggage. Thus the middle position is the most useful and versatile, offering
above-average compliance, sufficient ride-height, and adequate resistance to
bottoming.
And it is in those fast, sweeping corners where the K100RS really shines. Its
suspension squats evenly and predictably as the apex is reached, and mid-turn
corrections can be made with little effort. The bike is no featherweight, but it
carries the bulk of its heft which is the engine, primarily in typical low BMW
fashion. And so, despite its narrow, 24-inch-wide handlebar, the RS can be
flicked into a corner or side-to-side quickly and easily. You'll never be
tricked into believing that there's a 16-inch front wheel residing at the front;
but with its steep (27.5-degree) Steering Head Angle and short (3.9 inches)
front wheel trail, the RS is responsive and uncommonly neutral-feeling at all
lean angles, even when braking in a turn.
It's easy to see, then, how a rider can lock himself into a smooth, relaxed,
but extraordinarily fast rhythm on the K100RS without even trying
hard. That's a fair description of sport-touring, an activity at which the RS
performs brilliantly. The seating arrangement is better even than that of the
fabled R100RS sport-tourer, for while the two are roughly equal in the swervery,
comfort-wise, the K-bike is roomier and more luxurious for use on the open road.
The seat, for example, is padded with softer, thicker foam; and the footpegs
have been moved back ever so slightly compared with those on the Boxer, which
cants the rider a bit more forward and takes some of his upper-body weight off
of his tailbone. And the low, narrow handlebar is designed to keep the rider
tucked in behind the fairing so he's out of the airstream.
One interesting trick BMW employed to keep things calm behind the fairing is
the use of an adjustable airfoil just at the top of the windscreen. The foil
causes a venturi effect at the top of the screen, accelerating the flow of air
back toward the rider's head. This little wing does not enlarge the envelope of
still-air around the rider, but instead just smooths and directs the flow so
that the air that does hit the rider's helmet is relatively free of turbulence.
We have no wind-tunnel numbers to substantiate our feelings about the
aerodynamics, but we can attest to the fact that the fairing does an excellent
job of protecting the rider. One of our testers got caught in a sudden downpour
without his trusty rainsuit, but when he stopped he discovered that only his
boots and the top of his helmet had gotten wet.
That's the kind of thing that can forever endear the K10(?RS to its owner. So
too can a host of other well-thought-out niceties, such as: turnsignal housings
on the fairing which snap off easily in the event of a tip-over; a taillight
that can be popped off in seconds with no tools; an easily removable cam cover
and crank-case cover that feature self-centering bolts and reusable rubber
gaskets; a rear wheel that can be detached in minutes; and, of course, BMW's
highly acclaimed toolkit, which can actually handle some major engine work,
including crankshaft removal. Then there are some real BMW breakthroughs, like a
centerstand that is wide enough to provide stability when in use, and a
centerstand that not only can be deployed from the saddle, but that won't
retract unexpectedly and let the $7200 K100RS flop on it side.
What's more, the sidestand incorporates one of the slickest interlock devices
ever to hit the market. The sidestand is linked to the clutch via a separate
cable so that squeezing the clutch lever also automatically retracts the stand
if the bike isn't resting on it. If it is, the clutch lever simply won't move.
And since the engine will not start in gear without the clutch disengaged, BMW
has made it virtually impossible to ride away with the sidestand down.
BMW has also made it impossible for anyone, regardless of their allegiance,
to ignore the new K100. The bike has already been voted motorcycle of the year
in five European countries; in Germany alone, BMW motorcycle sales have
increased a staggering 120 percent since the introduction of the K100 last fall.
And with the recent export of the entire K100 family to the U.S., BMW plans to
increase its worldwide sales by more than 50 percent.
Ah, but to reach that sales goal, BMW figures that it will have to attract 35
percent of its K100 buyers from the ranks of Japanese-bike owners. And that's a
sword that can cut both ways. Because should the K100 prove too
successful, should this upstart motorcycle from Germany make any kind of a
noticeable dent in the market-share of the Big Four manufacturers, you can bet
your bottom Deustchmark on one thing: The Japanese will figure some way to flop
an inline-Four on its side and put together a K100-clone that'll sell for
thousands less. Maybe it won't be a good clone; maybe it won't take
sport-touring to a new all-time high the way the K100RS has; but it'll be
there, and the mere presence of a Japanese-built K100RS-replica could dilute the
market for such a bike just enough to cause big problems for BMW.
We hope it doesn't come to that. We hope that the Japanese will ignore the
small slice of the market that BMW might be able to capture and instead
concentrate on bigger, more lucrative segments of the sport. We're willing to
wager that they'll do just that. And so is BMW, obviously.
The difference is that we've got nothing riding on that wager. But BMW has
bet the whole store on it.
Source Cycle World 1983
Any corrections or more information on these motorcycles will be kindly appreciated.