Bimota KB4 and KB4RC
By Ben Purvis
It has been two years since Kawasaki's surprise announcement that it had bought a 49.9% stake in Bimota, and now we're seeing how the pairing will work going into the future - with the new KB4 and KB4RC going back to Bimota's earliest traditions of wrapping stock Japanese powertrains in a sharp-handling chassis.
Although the Tesi H2 was revealed alongside the Kawasaki deal, combining the supercharged H2 engine with Bimota's hub-steered Tesi chassis concept, the KB4 is a much more representative model. Its title follows directly on from the KB3 of the early 80s, and since Kawasaki looks set to provide all Bimota's engines for the foreseeable future, we can expect a KB5, KB6 and more to follow on without the near 40-year gap between the last two Kawasaki-powered Bimotas.
Kawasaki ownership makes its mark
Bimota built its brand around the idea of transplanting powerful, reliable Japanese engines of the 1970s from its original, uninspiring frames into stiffer, lighter bikes, but that niche was eroded as Japan's bike makers learnt how to make their own bikes handle well.
With the KB4 and the naked KB4RC (for 'Race Café'), the company goes back to the same idea, employing some radical thinking to regain the edge in terms of handling and weight reduction.
While the bikes take their 1,043 cc four-cylinder engines from Kawasaki's Ninja 1000SX, leaving them completely unaltered so they still pass emissions tests without extra expense, the 140 hp motors are bolted to a chassis that radically reduces the bikes' wheelbase - repositioning the radiator to a new spot under the seat. That means the front wheel can be moved back, leading to a short, 1,390 mm wheelbase and shifting the mass of the engine towards the front, all while retaining a long swingarm for good traction. Side-mounted ducts take air to the radiator.
The frame itself is part steel tube, part billet aluminium, with a purpose-made alloy swingarm and the usual combination of Öhlins and Brembo components for the KB4, while the KB4RC has been shown with Marzocchi suspension.
