A potentially serious problem with ethanol is that it can be incompatible with older rubber compounds. Also in higher concentrations it can cause corrosion to steel and aluminum that is a part of older motorcycle fuel systems.
I know that US regulations for cars have required ethanol-resistant materials for fuel for quite a long time, like several decades IIRC. Do you know if motorcycles are exempt from those regulations? If not, it seems the issue should be the same as with (ie no more serious than) old cars.
