When I lurk about how "eco-friendly" a motorcycle can be, I'm not thinking about a Harley-Davidson or something similar to that.
What comes in mind for a 3rd-world guy regarding cheap-to-run and fuel-efficiency is something like this:
Honda Biz, made in Brazil, currently available with a 125cc air-cooled engine with EFI and catalytic converter. In spite of the air cooling being often deemed inefficient, since it doesn't require a synthetic cooling fluid which will have to be blended with clean water and often replaced it still sounds more "sustainable" at the long run.
Or that
Honda NXR 150, also made in Brazil, and available with a flexfuel engine able to run on E100 or E96h ethanol, also air-cooled fitted with EFI and cat.
Or this one
Yamaha Ténéré 250, also made in Brazil, and fitted with another air-cooled engine with EFI and cat.
They still provide a fuel-efficiency comparable to some random hybrids, while their lifetime footprint from manufacturing to end-of-life disposal remains more energy-efficient than any subcompact car, and their emissions are not lower just per mile but also per gallon, since they're enforced to meet the same emission standards as a car.