Ethanol does affect some rubber items, but it's biggest problem is it's affinity to water. I often find gas tanks and carbs corroded from this. Also, since water is denser than gas, it may not pass through small jets. This can cause an intermittent lean condition with flat spots and poor throttle response. When you use any type of oxygenated fuel you should periodically use some type of drying agent. Just about anything that "cleans your fuel system" or "removes water" will work. I suggest Heet, STP, Prestone, etc. Remember to use it proportionately for the size of your motorcycle tank as compared to a car tank. Don't use the whole bottle at once. Repeat every 2 or 3 tanks.