Bimota YB6

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.

Source: Fast Bikes by Roland Brown