Kawasaki hybrid plans take shape
By Ben Purvis
With motorcycle manufacturers all over the world rushing to show their dedication to an all-electric future - mostly without actually going to the expense of launching any electric bikes - Kawasaki is following the example of some car makers by planning a hybrid bike as an interim stage before going fully battery-powered.
In the past, attempts at hybrid motorcycles have been few and far between. Piaggio made hybrid versions of the MP3 in 125 cc and 300 cc forms for a short while, and Honda more recently developed the PCX hybrid for sale in some Asian markets, but where car companies have wholeheartedly accepted the idea of combining battery and petrol power, bike firms have been largely uninterested in the format.
Traditionally, the reason has been simple: fitting two separate powertrains into a motorcycle, where every cubic centimetre of space is at a premium, hasn't provided a convincing advantage over simply making a cleaner, more economical petrol engine.
But with battery and motor technology improving and growing demands for vehicles capable of running in zero-emissions modes for city use, Kawasaki has re-evaluated that position and reached the conclusion that a hybrid might make sense after all.
All the indications are that Kawasaki will show its hybrid later this year, although it's not clear yet whether it will be as a production machine or simply a concept bike. The firm hinted at the hybrid with a brief video, released late last year, showing how such a bike could operate in petrol-powered mode out of town, switching to pure electric power in the city, and use both power sources when maximum performance was needed.
Since then, multiple patents have emerged showing aspects of the firm's hybrid development.
Unlike some earlier attempts, Kawasaki isn't making a scooter or a bike with a continuously variable transmission. Instead, the petrol engine is attached to a completely conventional multi-speed manual gearbox. There's simply an additional electric motor that's also geared to the input shaft via a short chain.
Because the motor doubles as the starter motor and generator, it offsets some of the additional weight and size that it brings, and it also means the petrol engine can be downsized, further reducing the packaging problems. Unlike a pure electric bike, the batteries do not need to be huge and heavy - the bike will only be expected to run in all-electric mode for a few miles at a time, and there's no concern over long charging times as the batteries will be topped up by the petrol engine, along with regenerative braking when the bike is cruising.
The most detailed patents seen so far show a parallel twin engine, probably related to the motor in the Z400 and Ninja 400, with the electric motor mounted above the gearbox. The brief view of the bike in Kawasaki's teaser video backs this up - proving that the prototype also uses the Z400's tubular steel frame.
Interesting aspects of the design shown in Kawasaki's patents include a 'boost' button on the throttle grip. A patent-worthy innovation in itself, since the switch turns with the throttle, so it's always under the thumb - the idea is that you can instantly call on the combined power of both the electric motor and petrol engine when overtaking acceleration is needed.
Although Kawasaki showed a poorly received all-electric prototype in 2019, the firm clearly stated that there were no production plans for the vehicle. However, the lessons learned from that electric bike project, which included the development of a bike-specific 20 kW drive motor, batteries, control software and regenerative braking systems, play perfectly into the development of the hybrid model that has been the follow-up focus for Kawasaki's R&D engineers.
