Yamaha Revisits Its Old Hybrid Ideas

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Yamaha is back in the hybrid motorcycle game it seems, with new patents showing variations on the “series hybrid” theme. (Japanese Patent Office/)

Kawasaki has already gone public with its plans to use hybrid motorcycles as a steppingstone between pure combustion models and electric-only machines but it might not be alone in adopting the idea. Yamaha—which showed an interest in hybrid bikes more than a decade ago—is revisiting the same concept but from a very different angle. There were hints at Yamaha’s renewed interest in hybrids back in 2020, when a new patent showed the thinking behind its next-generation system. Now a spate of new patents show that project appears to be expanding, covering multiple designs.

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A series hybrid also utilizes two motors but depends primarily on the electric motor to do most of the work. On this first scooter-style design, Yamaha places the battery and electric motor underneath the seat. (Japanese Patent Office/)

The upcoming Kawasaki, already shown in prototype form, is a conventional “parallel” hybrid. That means it’s effectively a normal, combustion-powered bike that gains an additional electric motor/generator that can be engaged or disengaged automatically or on demand. So it can run purely on gas power, as a solely electric machine with the combustion engine disengaged, or as a dual-powered bike with both drive units working simultaneously. The design also makes for a relatively conventional riding experience, with a normal gearbox, for instance, and in gas-only mode there’s no reason to think you’d notice anything out of the ordinary.

Yamaha’s earlier hybrid concepts included the wild Gen-Ryu from 2005, which used a continuously variable transmission to blend power from the electric and gas motors. (Yamaha Motor Corp./)

Yamaha, in contrast, has always shown interest in more radical hybrid tech. Back in 2005 the firm showed the Gen-Ryu hybrid concept and the HV-X in 2009, both using a hybrid system similar to that on Toyota’s original Prius. Yamaha and Toyota are closely tied, and at that stage the car firm had recently bought a stake in the bike company. The Prius-style system involved using a cunningly simple planetary gear to blend the power from a gas engine and an electric motor into a continuously variable transmission, as well as recovering energy under braking or when the battery needed charging.

The second of the new designs shifts the gas engine backward and relocates the electric motor on the swingarm, for a more compact machine. (Japanese Patent Office/)

Yamaha’s latest take on the hybrid idea goes in a different direction altogether, adopting the “serial hybrid” arrangement where the combustion engine’s only purpose is to run at an efficient speed to recharge the battery, with the electric motor doing all the work of actually driving the bike forward. The series hybrid idea isn’t as common in cars as parallel hybrids, although there have been examples, like the Chevrolet Volt, that have reached production. However, the idea itself is very old, having been used for decades in diesel-electric locomotives and appearing in ships as far back as 1903. Serial hybrids can, of course, run on battery power alone, with the combustion engine working as a range extender to allow the use of a smaller battery pack as well as having the same ease of refueling as a gas-powered vehicle.

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This patent highlights a reconfigured cooling system with the engine, motor, and generator all cooled by one shared radiator. (Japanese Patent Office/)

The first of Yamaha’s new designs is similar to the machine we saw patented back in 2020; a scooter-style bike with a low-mounted combustion engine powering a generator, a large battery mounted below the rider’s seat, and an electric motor, inverter, and reduction gearbox underneath that. The patent’s focus is on the cooling of the motor and electronics, with a radiator mounted in front of the combustion engine to draw heat away.

Second and third variations on the idea show generally similar machines. The second takes the same thinking but rearranges the components, putting the electric drive motor into the swingarm and shifting the combustion engine and generator backward as a result, creating a much more compact bike overall but at the expense of increased unsprung mass. It indicates how the same components could be used in a TMAX-sized maxi scooter—the first iteration—and in a smaller scooter more akin to the XMAX in size. The third version shows a scooter identical to the first, larger machine but with a reconfigured cooling system so the combustion engine, generator, and electric motor and inverter are all cooled by one, shared radiator.

Another big hybrid scooter, but also with a different cooling system utilizing two radiators instead. (Japanese Patent Office/)

A fourth design in the new patent shows a bike similar to the first, TMAX-sized scooter but with further updates to the cooling system. On this variant, there are two separate radiators, one for the generator engine and a second, larger radiator for the electric motor and electronics. The idea here is that the ideal temperatures for the two components differ—the combustion engine needs more heat to be economical, while the electric motor is at its most efficient when kept cooler. Further designs show different positions for the two radiators, suggesting that the unconnected cooling system is the version that Yamaha’s engineers prefer, but intriguingly they also illustrate a very different layout for the bike’s combustion engine and electric motor.

Other variations position the gas engine and electric generator well above the electric motor (air-cooled in this case). (Yamaha/)

Several images (fig.6, 8, 9, 10) all show bikes with the small combustion engine and its associated electric generator mounted high in the chassis, above the electric motor. Variations on the theme show an air-cooled motor (fig.8, 10) and a water-cooled unit (fig.9), as well as a variety of radiator positions including side-mounted (fig.6) and ducted versions (fig.9, 10).

Although the patent goes to show that this sort of bike is still a long way from production, with some elemental differences in layout and configuration still under consideration, there’s no doubt that Yamaha’s engineers are looking at the idea of hybrids. With increasing pressure from governments around the world to cut back on the reliance on fossil fuels and several countries planning outright bans on the sales of new cars that aren’t either electric or hybrid in just a few years’ time, Yamaha—and all bike firms—know that a strategy to shift toward electric or partially electric models in the midterm future may be vital to their survival.

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