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Bimota HB2

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Make Model |
Bimota HB2 |
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Year |
1982 (production 193 ) |
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Engine |
Air cooled, four stroke, transverse four
cylinder, DOHC, 4 valves per cylinder. |
|
Capacity |
901 |
|
Bore x Stroke |
64.5 X 69 mm |
|
Compression Ratio |
8.8:1 |
|
Induction |
4x 32mm Keihin carbs |
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Ignition /
Starting |
Inductive electronic / electric |
|
Max Power |
95 hp @ 9000 rpm |
|
Max Torque |
77 Nm @ 8000 rpm |
|
Transmission /
Drive |
5 Speed / chain |
|
Frame |
Tubular steel space-frame |
|
Front Suspension |
Italia with 8 settings with
magnesium tubes |
|
Rear Suspension |
Slightly backward facing De
Carbon shock absorber with 10 settings. |
|
Front Brakes |
2x 200mmdiscs |
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Rear Brakes |
Single 200mm disc |
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Front Tyre |
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Rear Tyre |
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Dry-Weight |
200 kg |
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Fuel Capacity |
|
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Top Speed |
231 km/h |
Bimota's exotic HB2. with its rounded half-fairing, one-piece
tank-seat unit, aluminium frame sections and rising-rate rear suspension
unit, seemed like a motorcycle from a different planet when it was launched
in 1982. The sleek Italian superbike's Japanese rivals were mostly naked
fours with steel frames and twin shocks. Even Honda's mighty CB1100R was
almost old-fashioned by comparison.
The HB2's initials stood for Honda Bimota, and its engine was the
air-cooled, 90Ice twin-cam engine from the Japanese giant's CB900F. In
Bimota style the 16-valve motor was left standard, complete with its bank of
Keihin carbs and airbox, although some owners fitted larger flat-slide
Mikunis. Bimota's twin-silencer exhaust system saved some weight but barely
increased the standard 900F's output of 94bhp. The big motor was partially
covered by the Bimota's half-fairing, which blended with the one- piece
tank-seat unit. (This could be removed after undoing just four bolts plus an
electrical connector.) The screen was usefully tall and protective; the view
from the rider's thinly padded single seat was of a top triple clamp
machined from a solid chunk of lightweight alloy. Stiff and lightweight
frame When the tank-seal unit was removed, the quality of the HB2 became
clear. The frame's visible steel tubes, which ran down to join the alloy
plates at the swingarm pivot, were backed up by numerous smaller tubes
around the steering head. The aluminium plates at the swingarm pivot
provided strength and light weight in that crucial area. A De Carbon rear
shock, vertically mounted and operated via a rising-rate linkage, replaced
the 9()0F's twin shocks. Front suspension was exotic, too: a pair of Ceriani
telescopic forks with gold-finished sliders and. at the top of the legs,
adjusters that could be turned by hand.
In combination with the Bimota's reduced weight - at 441 lb (200kg) it
was over 70lb (32kg) lighter than the CB900F - that gave a substantial
handling advantage. The suspension worked superbly well, giving a taut yet
also very comfortable ride. Other high quality parts included five-spoke
alloy wheels, produced in the 16-inch diameters that were popular in grand
prix racing at the time. The front brake set-up of twin-piston Brembo
calipers and drilled 280mm discs was state of the art. as was the fat
Michelin rubber.
And the Italian bike was superb in a straight line. too. At low revs the
Honda engine impressed with its smoothness and torque, especially with the
original CV carbs in place. There were no glitches Original Bimota: the HB1
Bimota's first ever bike had also been powered by a four-cylinder Honda
engine. The first HB1 was built from the wreck of the CB750 that Bimota
design ace Massimo Tamburini had crashed at Misano. With its
racetrack-derived styling and rigid tubular steel frame, the HB1 was a
stunningly advanced machine when unveiled in 1972. Only ten examples were
ever produced. or stumbles as the Bimota purred forward at a fearsome rate.
Unlike the standard Honda, the HB2 had the fairing and the tucked-in riding
position to make cruising speeds of lOOmph (I6lkm/h) or more hugely
enjoyable for almost as long as its rider dared. And the HB2 remained
impeccably stable as it headed towards a top speed that one magazine tested
at I38mph (222km/h).
Fewer than 200 examples of the exotic HB2 were built, plus a further 100
units of its similarly styled successor the HB3. which was powered by the
engine from Honda's CB1100R. The HB3 was produced until 1985. by which time
the Japanese manufacturers, too. had introduced fairings, aluminium frames
and monoshock suspension. In typical Bimota style, the HB2 had led the way.

Nestled in a fold of the South Downs is a sleepy village in the middle of
which is an old pub with a thatched roof. The tranquil picture postcard
image is deceptive, however. The fact is the adjacent square miles contain
some of the most testing bits of tarmac for hustling bikes. A combination of
country lanes winding through hills and valleys, tight tree lined turns,
hump backed bridges and for good measure a new motorway classed road that
has been pushed through to take the sightseers down to Portsmouth. Many
expensively produced and lavishly promoted makes have found their Waterloo
upon these roads. A few, very few, have excelled. On balance the roads have
usually defeated them. Until now! Now the yardstick has been broken the book
of comparisons thrown out of the window. The Bimota's have changed all that.
Even to try a comparison with other machine is pointless. They are so
totally different. You can only try to describe them and begin to comprehend
what they are about. They are simply a different concept in motorcycling. It
is a mark of how far we have gone down the road of mass marketing for Mr
Average that the Bimota's are so unique and so specifically superior.
Specifically, because in overall consumer terms there are a number of
important disadvantages to owning one, not least the price, and in fact you
would be too scared to park it anywhere less secure than a locked concrete
bunker.
A bimota is a very basic motorcycle. There are no mirrors, no indicators,
no pillion seat, no luggage space, and only enough room for the pilot if he
is prepared to stretch and squeeze his body into the position the machine
demands. It is uncompromising, uncomfortable, anti social, and impractical.
It is also the most incredible exhilarating and beautiful experience on two
wheels other than winning the 500 cc World Championship. Compared to that
the bimota is cheap.
Let us go back to the motorcycle as a concept. The Japanese view is that
the machine is a method of transport, a means to an end. This is inevitable
because it was the whole reason for the establishment of their two-wheel
industry. They were not enthusiasts who wanted to go racing and experiment
with engines and chassis design, they were practical businessmen who worked
methodically to provide mobility for a nation and eventually half the world.
If it could not be conveniently made, and profitably sold. It was not worth
considering. To reach the maximum number of customers, a bike is built with
the broadest possible appeal at the cheapest acceptable cost, If that means
cutting corners and accepting lower standards in material and design, that
is all accounted for in the eventual price.
A large part of that price in any case is the cost of promoting and
packaging the product - convincing Mr Average that this really is what he
wants to ride this year. Next year of course he will have to buy something
else because fashion will convince him it is out of date.
Bimota's are not on the mass production merry go round. True they keep
innovating the two new frame kits are a testimony of that. But even a
four-year-old bimota looks advanced and futuristic to its rivals. Bimota do
not see motorcycles as a means of transport, it is not a means to an end,
and it is an end in itself. It is perfection, which is the goal. Whether it
is generally acceptable or affordable does not particularly bother them,
theirs is a statement of fact, not fashion or frills.
Take the lack of pillion seat as an example. It is not because of an over
large petrol tank or a boy racer seat, it is because the perfect motorcycle
can only be designed to carry one person and he is already seated as low as
possible to keep the centre of gravity down. If bimota wanted a two seater
they would have to redesign the whole chassis. The design concept is carried
through into production without being modified or compromised by
consideration of cost or simplicity. Just look at the naked bones of the two
new bikes reveals the awesome truth. Unlike most bike frames which are
simple cradles or spines, with bits tacked on to carry the extras, the
bimota is a jigsaw puzzle of cross braces, using short tubes in a
triangulated pattern with very little bending as such. It is a principle
much used in aircraft construction because it avoids stress, which is
inherent in long tube runs, which are bent, and then have to be gusseted at
the joints for strength. There are hardly any gussets on a bimota frame. All
the joints in the chrome moly steel tubes are made to take directional
stress end to end along each tube, not only as joints themselves. The tubes
may be compressed but they will not twist nor will they flex. The price of
this rigid construction is complexity. The KB2 frame for the 550 Kawasaki,
for example, has 44 individual tube members from the steering head to the
swing arm pivot. This means pains taking welding on a precise jig - a very
time consuming job for a craftsman only. Despite its web like appearance,
the frame is in fact a cradle. It is just that it cradles the engine from
side to side, not to bottom, keeping the height down whilst giving clearance
underneath for the exhaust pipe. With the tank and seat removed, the rolling
chassis is a virtually mobile workbench, allowing a top end overhaul with
ease - something the Japanese tend to forget about. The only thing that is a
bind to reach on the KB2 is the gearbox sprocket, which is behind the swing
arm pivot. Outrigger forgings house the swing arm bearing directly in line
with the countershaft sprocket to give perfect chain tension through swing
arm movement. Bimota have done away with this on the HB2 frame for the
bigger Honda engine, not so much for maintenance as to keep the overall
width to acceptable levels. The Honda has a massive clutch housing on the
right hand side of the crankcase, which would require too much hardware to
clear. Instead they have gone for a neat alloy casting behind the engine
which replaces frame tube members at the base of the cradle. The intricately
connecting tubing of both frames forms a straight line between steering head
and the swing arm axis, giving maximum rigidity between the two main load
bearing pivots. The engine is just shoe horned into the cradle formed by the
two spars of the backbone. When it is exposed, the Honda motor is revealed
in all it's glory with it's cobby double cam boxes and the threatening open
bell mouths of a bank of four 33mm Mikuni slide carburettors. Just
stationary in the workshop it is a thing of real beauty, a solid structure
of engineering finesse.
The HB2 chassis is obviously higher and wider to cope with the larger
powerhouse beneath and inside it, but other than that there are a similar
number of components. The rear suspension system is a particular bimota
innovation. The Japanese first introduced rising rate systems on production
Motor cross bikes two years ago. Bimota introduced one that works in 1975.
It has been moved around in the chassis quite a bit because of the variety
of frames, but the essential single De Carbon unit arrangement is retained.
It is compressed at both ends, being mounted nearly upright, with an
aluminium rocker arm levered by pushrods mounted on rose joints above it.
The set-up gives an exceptionally high leverage ratio of 8:1 (rear wheel
movement to damper rod action) which gives precise control; but makes it
particularly difficult to set the shock correctly for rider weight and
riding style. A small adjustment of the shock translates into a much bigger
alteration in wheel travel. A continuous thread sets preload, and a click
stop knob gives both ten compression and rebound damping settings. Such
great leverage imposes much higher stress on the frame than conventional
twin shocks. Therefore it is doubly important that the chassis is integrated
with the system instead of just having it bolted on the back for reasons of
fashion. The essential difference between Bimota's system and that used on
some large Japanese sportsters is that Bimota's woks better the j=harder it
is pushed. That is the way Bimota's are designed and that is the way they
work. The majority of modern super bikes have a high centre of gravity, long
travel suspension and an excess of power. The combination, while technically
impressive, is potentially highly unstable in inexperienced hands and often
barely manageable even in experienced ones. The sobering thing about riding
a bimota is that it has achieved such a perfect balance of those forces. You
have to learn to ride all over again - or more to the point, un learn a lot
of the instinctive reactions bred by relatively poor handling machines.
There are other, lighter machines with less horses that can approach a
similar standard, but bimota have harnessed the giant Japanese power houses
and made them work in a motorcycle. It is a development that has historical
validity with a sounder basis than the sketchy memories of those who just
seem to remember that bikes did handle better in the good old days. They
did, but not through any particular ancient wisdom - the simple fact was
that they generally less power and weight to cope with compared to nowadays.
It is almost indecent to comment on what it is like riding a bimota,
revealing secrets shared by so few. It is harder still to put the experience
into adequate words, so often misused by the bland description of other mere
motorcycles. How do you compare them? By how much do they steer better?
handle better? brake better? There is no suitable graph on which to plot the
relative performance; other than to say that all comparisons are irrelevant.
On a scale from 1 to 10 the Bimota's come in at around 15. The only
reasonable contrast is between the tow models. I rode the Kawasaki first,
some time back, and it felt big and strange. You just cannot sit on a bimota
and cruise around on it. You are forced to conform to it, squeezing your
legs onto the footrests, backside into the seat and dislocating your
shoulder blades to reach the handlebars. This is called assuming the riding
position. Once there, very little else you do seems to make a lot of
difference to the bike. It knows it has got you where it wants. Now it is in
control. You think you have a hold of the throttle, you think you are using
the brakes properly, but the bikes just sat there chuckling away underneath
you because it knows it is not even trying. Like the GPz550 engine, which is
its heart, it thrives on revs. The KB2's motor has a 600 conversion,
although it is not noticeably more powerful, probably because of the
slightly higher overall gearing to make use of the bikes aerodynamics, in
fact if anything it is underpowered, due to the excess of handling
performance. Once you are into the feel of the thing, you find you can use
all of its rpm because the chassis can cope. In comparison, the Honda feels
like a monster. Once your limbs and tendons have been stretched and
contorted by the KB2, they are ready to be further extended by the
additional bulk of the HB2. It feels big; it is big, the weight being
evident in slow speed manoeuvring. After the KB2, it takes a bit of getting
used to. Actually on the road, and at speed, those extra pounds are a help
in some circumstances as they press the bike more firmly on the tarmac. The
KB2 may start to skip on some bumps under acceleration - the HB2 just
thunders over them. Its additional power, of course, is equally dramatic.
Although the conversion will accept standard carbs and airbox, our test bike
had Mikuni racing units and open bell mouths, creating a gorgeous burbling
beneath the tank. They do not like having the throttles yanked open, so
swapping from the fast revving Kawasaki model needs little bit more finesse,
but once under load it surges like a stream train. It is outrageously fast
in a straight line, but the thing that takes longer to appreciate is that it
is extremely rapid through turns. All turns not just long sweeping ones, you
can apply the power smoothly, though tight fiddlely turns where a smaller
bike may have an edge. What bimota have done is made a 900 handle like a
500.
One of the secrets of the new generation Bimota's is matching all that
frame and engine technology to 16 inch wheels, and making them work. It is
something that few, even in racing, have so far satisfactorily achieved. The
16 inch wheel gives you not only a much lower bike with a better centre of
gravity, but a five inch spread of rubber at the front and six inches at the
back. The V rated Michelin tyres are big, in fact, their rolling diameter is
not a lot less that a conventional 18 inch wheel, but the overall contact
area is so much greater. Compared to them a normal Superbike wheel looks
like it has come off a bicycle. The tread on the rims gets the power down at
all angles, and allows use of the full force of the three 11 inch Brembo
discs. Either stopping or starting the potential is awesome. The only
drawback at the moment is that there are no alternative tyres, and the
shallow treads of the Michelins will not last long with road use. In the
future most big road bikes may have 16-inch rims, but it will be a long time
before they catch up with Bimota's expertise. The reason why they work is
that a smaller diameter requires less leverage on the steering making the
bike more responsive and easier to change direction. The problem is that the
whole chassis has to be designed to handle that potential if it is not going
to become an unstable flying hinge. How far bimota have integrated that
principle is evident when looking at the bare chassis and engine. Despite
the fact that they have got the whole bike as low as possible on it's small
wheels, they have still got the bowels of the engine - it's heaviest point -
close to the axle line. If it were much lower, the bike would stand up on
it's own. A further trick at the steering end is the offset yokes. The fork
yokes are not parallel, but four degrees out of line, the bottom one being
further away from the headstock than the top. This slightly pushes out the
stanchions, compensating for the reducing trail under heavy braking. Just a
little touch, a couple of degrees, but all part of the precision of
perfection. The Bimota's bristle with such niceties, from fundamental
design, to almost trivial detail like flush fitting Allen headed bolts, and
beautifully milled aluminium brackets. Bimota does not cut corners, instead
of running unsightly pipes and plumbing for the brake hydraulics, they drill
the yokes to act as a junction box.
There are no superfluous features on a bimota. The gulf is now wider than
it was a decade ago when Hailwood and Agostini were locked in a titanic
battle for 500 cc honours in racing. Even then the contrast between the
approach of the Honda and MV factory could not have been more apparent. In
order to combat the evidently superbly handling Italian machine, Honda's
solution was an engine with even more power. The theory was logical enough.
If it went fast enough down the straights it ought to be far enough ahead by
the turns. Unfortunately the end result was a bike that went slower through
the corners because it handled so badly. So it lost all the advantage it
gained on the straights. How satisfying for Hailwood when a supposedly
outdated Ducati in the Isle of Man more than ten years later, he could
remind the Honda team that they still had not learnt the lesson? Perhaps the
final comment worth considering is from someone whom had never seen a bimota
before, and knew nothing about them. Mick Whitlock has never been to a road
race and barely ridden a road bike, though he has spent all of his working
life involved with motorcycles. He works in the equally precise world of
trials, building what is generally reckoned to be the finest chassis kits
for one of the most demanding sports. I took the KB2 round to show him, and
let him look it over. He did not look at the tank or the fairing or the
paintwork. He studied the engineering, and the quality, and knew the hours
spent. Then I told him the price. "Yes" he said "I can see why".
Source Bike magazine from November 1982
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