TOKYO — The Toyota-led push to plug hydrogen combustion as a path to carbon neutrality has gained backing from rivals such as Honda and Suzuki as a group of Japanese minicar and motorcycle makers launch a fresh nationwide effort to promote the technology.

Honda Motor Co. and Suzuki Motor Corp. will join Kawasaki Motors and Yamaha Motor Co. to develop hydrogen combustion engines for “small mobility,” a category they say covers minivehicles, motorcycles, boats, construction equipment and drones.

The new effort, announced Wednesday, injects fresh energy into a clean powertrain strategy championed by Toyota Motor Corp., which has largely been a lone voice in the wilderness on the technology.

Toyota Chairman Akio Toyoda has been positioning hydrogen combustion as one route to achieving carbon neutrality since 2021. Japan’s biggest automaker has been developing hydrogen-burning engines and deploying them in race cars, and the Toyoda is expected to take his turn behind the wheel of one in an endurance race at Fuji Speedway this month.

As recently as 2021, Honda CEO Toshihiro Mibe had shrugged off the potential of hydrogen-burning engines. He said Honda had studied the technology but didn’t see it as feasible for cars.

Now Honda seems to be changing its tune.

Honda, Suzuki, Kawasaki and Yamaha said in a joint statement they will form a new research association called HySE, short for hydrogen small mobility and engine technology. Toyota will serve as an adjunct member of the group, drawing on its research for use in larger vehicles.

“Research and development targeted at commercialization of mobility with engines powered by hydrogen deemed a next-generation energy source is gaining momentum,” they said.

The partners will pool their expertise and resources with the “joint mission of establishing a design standard for small mobility’s hydrogen-powered engine.”

All four companies are major motorcycle manufacturers and makers of marine engines for boats and craft such as jet skis. But Honda and Suzuki are also top makers of popular Japan-specific minivehicles, which comprise nearly 40 percent of the domestic four-wheeler market.

The new drivetrain is not a hydrogen fuel cell technology that generates electricity.

Rather, the proposed powertrains rely on internal combustion, burning hydrogen instead of gasoline. The potential benefit is near-zero carbon dioxide emissions.

While touting the development’s potential, the new partners also acknowledged big challenges.

Hydrogen burns fast and has a wide region of ignition, often resulting in unstable combustion. And there is limited storage capacity for the fuel, especially in smaller vehicles.

“In addressing these issues,” the group said, “the members of HySE are committed to conducting fundamental research, capitalizing on their wealth of expertise and technologies in developing gasoline-powered engines, and aim to work together.”