| Designer | Massimo Tamburini | ||
| Production period | 1974 – 1975 | Production number | 20 thereof 15 kits |
| Power | 37 KW (50 PS) 44 KW (60 PS) | Displacement | 249 cc 349 cc |
| Topspeed | je nach Übersetzung | Gewicht | dry 95 kg |
| Technical basis | Yamaha TZ 250 / 350 |
In early 1974, Bimota decided to produce a racing chassis in small series and sell it to interested racers. The chassis was designed for the Yamaha TZ 250 and 350 engines, which were widely used in the corresponding racing series at the time. Unlike the frames of the HB1 and PB1, the YB1 frame is a closed double-loop frame, reinforced above the engine with two cross tubes between the upper and lower frame tubes. The rear frame is welded to the main frame. Despite its high rigidity, the frame is very light. At just under 6 kilograms, it weighs about 4 kilograms less than the original Yamaha frame.
The YB1 frames are mostly offered as kits, with additional components. These always included the box swingarm and, in the first models, Borrani spoked wheels and a 35 mm Ceriani fork. An aerodynamically designed fairing, which is wide enough to enclose the clip-on handlebars, was available as an option. A monocoque, i.e., a single-piece cover for the tank and rear frame with an integrated rider seat and rear spoiler, was also available.
The YB1 was used extensively in national and international championships and achieved numerous racing successes, particularly in the 350cc class. Riders like Giuseppe Elementi, Mario Lega, and Roberto Gallina secured many podium finishes and even a victory in the 350cc World Championship in 1974. In 1975, Johnny Cecotto won the 350cc World Championship on a Yamaha with a Bimota frame. The successes of the YB1 formed the foundation for Bimota’s further rise in the racing scene.
It is important to note that in the 1970s, many racing teams used custom-built chassis from manufacturers who received little attention outside the paddocks. For example, Johnny Cecotto, as a rider for the Venemotos team, the Venezuelan Yamaha importer, won on a Yamaha Yamaha, not a Bimota or Yamaha-Bimota. In addition to Cecotto, Swiss rider Bruno Kneubuhler and Italians Otello Buscherini and Mario Lega used the YB1 frame in the 350cc World Championship. This shows the reputation Bimota had quickly built for itself in the racing scene.