Most U.S. states currently allow up to 10% ethanol in gasoline formulations, Michigan included. I've not noticed any problems with the 10% blend, but it sounds like the EPA may allow this to be increased to 15% in a few months after further testing. Are there likely to be any negative side affects (to components) to our old bikes at 15%?
The only side effects that I can think of, besides the reduced HP this fuel will bring (and resulting lower MPG) are [potentiall] increased wear on the valve seats and more-easily rusted gas tanks and mufflers: see comments below. There's nothing else in these engines that will be affected.
The valve seats in these engines are fairly soft, which has been their saving grace. When fuel went unleaded, Ford led the charge to VERY hard valve seat inserts, which the rest of Detroit took up (starting in 1969). Detroit engines with pushrods all spin the valve a partial turn on each opening, so as to help clean the seats: this needs lubrication or else the valve grinds itself into the seat over time. Honda took a different tack: they installed Stellite exhaust valves in the 350 twins, then the 750 and all the SOHC4 bikes, while stopping the rotation of their valves altogether. By installing soft valve seats, the crud that Detroit grinds away ends up slightly embedded in the Honda seats, instead. When the engine gets hot enough, it burns these deposits off (this burnoff is not possible in a water-cooled engine, BTW). After many miles of this activity, some pitting can occur that leaks across the seat area, and the valves leak. (This is why I added Honda's old "Valve Maintenance Rules" in the Appendix of my book. This was considered 'normal maintenance' in the day.
) Increased alcohol in the fuel will lower the combustion temperatures, which just means you have to ride further to burn off those deposits...
The alcohol draws moisture out of the air and it turns into water in the lower parts of the gas tank. Water has a strong affinity for the uncoated steel in the tanks, so it tends to rust the surfaces that are not covered with fuel. Since gas itself is really oil, it prevents rust if the steel is wetted with it. So, when storing these tanks, I always fill them all the way up, then drain the system from the float bowls in the Spring, to remove the water at the bottom. And, once each week I go to the petcock and open it up to refill the bowls. This tends to keep the water out of the tank itself, and keeps the fuel from crystallizing in the bowls: this is called "wet storage" and works well. If you drain the tank, you must also coat the inside with oil spray (CRC is good, WD40 only sort of good, as it draws water, too).
When alcohol burns, it produces the water vapor that it absorbed. This puts the moisture into the exhaust system. This again means that you must ride far enough to heat up the whole pipe(s) so as to burn off the water....
When viewed conspiratorially, it does appear that the [corrupt] powers that be are trying to push older vehicles off the road. When viewed politically (as in, 'follow the money'), it is much simpler and a little more accurate: during the last election, the current crop of Dems promised farmers in Iowa and other corn-growing states that they would increase the required amount of ethanol in gasoline to support their corn. They also promised the UAW that they would mandate people to buy more of their cars. The Repubs declared that increasing the ethanol would be hard on refineries (it is) and people's pocketbooks, because of reduced MPG (yah), so they did not support the idea. 'Nuff said?
