As you say, lots of guys pushing around older air-cooled iron (think old Triumphs, Nortons, BSAs and such) swear by routinely adding a splash of 2-stroke to their fuel, and it seems to do them the power of good. It's also just the ticket for older fixer-upper bikes or other vehicles being resurrected after not having run in a long while. I myself run an ounce or so (about 30 ml) of something called Marvel Mystery Oil per tankful of fuel in my primitivo-design "Iron Belly" Bullet. I premix it in 89 octane (as per R+N/2 measurement used in USA) ethanol-free with some StaBil 360 fuel stabilizer as well. Unlike my other more humdrum vehicles that just get that regular 10% ethanol spew at the pump, my Bullet's on a steady diet of the good stuff from fuel cans, as are my outboards, generators, mower and other small engines.
Now, whether adding 2-stroke or anything else to the fuel of a more modern engine like yours is a good idea, what with its finicky catalytic knick-knacks and electronic fripperies is debatable. My 2005 Bullet is actually the newest vehicle I own, so I don't know how much solid guidance I could offer anybody with a vehicle warranty. I frankly doubt I'll ever have one. I guess I'm just not a "new car smell" kinda guy.