Four
stroke, transverse four cylinder, DOHC, 5
valves per cylinder.
Capacity
989 cc / 60.4 cub. in.
Bore x Stroke
75 x 55 mm
Compression Ratio
11.0:1
Cooling System
Liquid cooled
Induction
4x 38mm Mikuni BDST
Ignition
-
Starting
Electric
Max Power
103 kW / 140 hp @ 9000 rpm
Max Torque
107 Nm / 11.5 kg-m / 78.9 lb-ft. @
8500 rpm
Transmission
5 Speed
Final Drive
Chain
Frame
Two diagonal beams in section bar made of
aluminium with internal ribbing. The cylinders are supported by plates
bolted to the beams and the swing arm is made of aluminium
Front Suspension
42mm Marzocchi forks, anti dive system in the
left tube of the fork leg and a hydraulic brake in the right. compression
and rebound damping adjustable. adjustable by four positions
Rear Suspension
Marzocchi single shock, compression and rebound
damping adjustable.
Bimota's YB series machines were among the finest sports
bikes of the late 1980s, combining powerful four-cylinder Yamaha motors with
the twin-spar aluminium frame layout that would be adopted by major
manufacturers in subsequent years. To that basic format the small Rimini
firm added sharp styling, high-quality cycle parts and top-level racetrack
development, plus the exclusivity that came with a bike that was hand-built
in very small numbers. The story of Bimota's Yamaha-engined four began
in 1987. when factory rider Virginio Ferrari won the Formula One world
championship, then the leading four-stroke race series. Ferrari's YB4 was
powered by Yamaha's liquid-cooled 20-valve FZ750 engine. Bimota's subsequent
YB4 El roadster was a replica of Ferrari's machine, and was quickly followed
by a similar YB6 model using the larger engine from the FZR1000. Unlike the
YB4, whose EI initials signified that it was fuel-injected, the YB6 used
carburettors.
The YB6 was a big success and was followed a year later by the
YB6 EXUP model, also known as the YB8. following Yamaha's release of the FZR1000 EXUP. This combined an uprated engine plus the new EXUP exhaust
valve that increased mid-range power delivery. As usual. Bimota retained the
Yamaha engine in standard form, but added a less restrictive silencer
that added a claimed 4bhp to the power output, giving a maximum of 147bhp at
10000 rpm. Like the standard YB6. the EXUP version used a YB4 style frame
with rectangular-section aluminium spars. Front forks and the rear shock,
complete with remove reservoir, were from Italian specialist Marzocchi.
Four-piston Brembo front brake calipers gripped huge fully floating discs.
The riding position was racy, with low clip-on handlebars, high footrests
and a thinly padded single seat. Compact and aerodynamic Along with
its slightly increased power, the YB6 EXUP was more compact and aerodynamic
than the standard FZR1000 as well as 50lb (23kg) lighter.
That meant that
it was probably the fastest and hardest-accelerating production motorcycle
in the world. Its smooth, high-revving power sent the Bimota storming to a
top speed of I70mph (274km/h). Equally impressive was the big 20-valve
Yamaha motor's smooth, torquey feel throughout the rev range. Given the Bimota's race-developed background and its close links to the factory YB4.
it was no surprise that the YB6 EXUP was very stable even when approaching
its maximum velocity. And it also handled superbly at all speeds. Steering
was light and neutral, grip from the fat Michelin radial tyres immense,
ground clearance absolute. The brakes were excellent, too. with a
combination of bite and feel to rival the very best. The extra torque and
refinement of Yamaha's new motor had added the finishing touch to make a
magnificent sports bike. Inevitably the YB6 models were also hugely
expensive.
Despite that they were a success for Bimota. which built a total
of more than 650 over the next few years - a large number by the standards
of the tiny Rimini firm. Tuatara - World's Fastest Lizard Bimota produced an
even more exotic variation on the YB6 theme in 1989, with the Tuatara model
of which only 60 units were built. This bike, named after a lizard that was
one of the world's slowest animals, was powered by the previous 989cc Yamaha
FZR1000 engine, fitted with a Weber-Marelli fuel-injection system in place
of carburettors. The result was a claimed peak output of 152bhp at 9500rpm.
Other changes included upside-down Marzocchi forks, ultra-light magnesium
wheels, and a futuristic digital instrument console. Bimota claimed a top
speed of 180mph (290km/h), which proved highly optimistic. But very few
things, on two wheels or four legs, were faster.