Kawasaki Developing Hybrid Motorcycle Technology

Common car technology could make it to two wheels.

hybrid drivetrain patent drawing
Kawasaki has submitted patent drawings for a motorcycle hybrid drivetrain with an electric motor residing above the transmission.US Patent Office

On four wheels, hybrid technology is increasingly being embraced as the convenient middle ground between gas-guzzling combustion engines and all-out electric power. Offering vastly improved economy and emissions without the range anxiety of a battery-powered electric vehicle, hybrids are offered by almost every automobile manufacturer on the planet, but so far the idea has completely failed to make the transition to two wheels.

It's not for a lack of effort. All the big Japanese companies have dabbled with the idea of hybrid bikes, combining conventional gas powertrains with a battery-powered boost from an electric motor, but despite making prototypes and concept bikes, production versions are notably absent. Only Piaggio has made the effort to go that far, building hybrid versions of its three-wheeled MP3 and classic Vespa scooter as much as a decade ago, but neither had a huge sales success. Now a new patent application shows Kawasaki hasn't given up on the idea, showing how the firm believes it can combine a conventional combustion engine with an electric motor.

Patent drawing new Kawasaki hybrid
Although the drawings are simplistic, the location of the motor, battery, and fuel tank are defined.US Patent Office

It’s hard to make out much detail from the patent. Its illustrations are simplistic, showing a single-cylinder design and a variety of potential layouts for the fuel tank and battery, but the idea actually falls into line with a much older Kawasaki design that dates back a dozen years.

The idea is very simple. An electric motor sits on top of the bike’s transmission, providing additional power and torque on demand. But the patent also demonstrates the major problem with hybrid bikes: where to put all the extra components. Cars usually have plenty of luggage space, so stealing a bit for a battery and electric motor isn’t a big problem, but motorcycles are incredibly tightly packaged. Every spare inch and pound counts, so lugging around a load of electronics—effectively accounting for a complete second drivetrain—isn’t easy.

Kawasaki’s illustrations show a machine with the battery and control electronics mounted where the fuel tank would normally go, while the tank itself sits under the seat. In another variation shown in the same document, the gas goes in a small tank to the side of the battery. The implication is that the electric element of this bike is more important than its conventional combustion engine, making this more like a range-extender electric vehicle than a mild hybrid.

Kawasaki drawing showing a battery in place of the fuel tank
One drawing from Kawasaki shows the battery residing where the fuel tank would normally be with a smaller fuel tank to the side.US Patent Office

However, the layout isn’t dissimilar from a design Kawasaki patented back in 2007 when it was looking to use hybrid technology to increase performance rather than boost fuel economy. The design was based on a Ninja ZX-6R, but it similarly had an electric motor positioned above the transmission. The idea was that the motor, which was connected to the crankshaft by a chain and a clutch mechanism, could double as the bike’s starter and generator but would also be engaged to drive when additional power and torque was needed. As a temporary booster, it required only a small, light battery.

At around the same time, several other Japanese firms also looked at hybrid tech. Honda experimented with Gold Wings using smaller four-cylinder engines and a crankshaft-mounted electric motor to make up for the two lost cylinders. That prototype design was eventually shown in the firm's 2015 Neowing concept bike, but there's still no sign of a production version. Honda also developed hybrid technology to fit to the NC750 parallel twin, but again, there's no hint of a production derivative.

2007 patent of ZX-6R
A 2007 patent drawing based on a ZX-6R showing a small electric motor used to boost performance on demand.US Patent Office

Suzuki has similarly played with hybrids, though like Kawasaki’s 2007 ZX-6R-based design, the focus was on performance rather than emissions or economy. Several years ago Suzuki patented a design for a GSX-R-style four-cylinder sportbike with an electric motor/generator unit and underseat battery that could deliver a boost when more power was called for.

And Yamaha, like Honda, has shown hybrid concept bikes including the 2005 Gen-Ryu and 2009 HV-X. The latter briefly appeared to be set for production before the firm lost interest in the idea.

At this stage it seems the fast-improving field of pure electric motorcycles means two-wheeled hybrids could be a missing evolutionary link that never really gets off the ground, but Kawasaki’s new patent application shows the idea of hybrid bikes isn’t quite dead yet.