I was in Beach Boulevard Yamaha when I was in Jacksonville. Bought tires there for my Liner. My buddy bought two bikes there. I do remember they recomend premium fuel for all bikes. I used it in my 1100 for a while then went back to regular.
This discussion had has gone on here and other blogs for ever. And not solved. Lately I saw where premium contributes to blueing of exhaust pipes. But I have seen that premium burns cooler. We do know it burns slower.
There seems to be no noticable advantage to premium and no loss of anything with regular if the bike is recomended for regular. So if you do not gain mileage or performance why spend the money? For my Liner Yamaha recomends premium so I use it. The cost is only 60 to 80 cents per fill up so money is not an issue.
I see Harley recomends premium for their bikes now.
My thought, use what the manufacturer recomends, they are the ones with the funny shaped heads.