According to the epa, e15 can not be used in on or off road motorcycles :
https://www.epa.gov/fuels-registration-reporting-and-compliance-help/e15-fuel-registrationNow I’m sure someone will say just find a station that sells e10 or even alc free. Easier said than done .
In my area, there are only two stations ( 40 miles apart) that sell E0. It is regular 87 ( not approved by Kawa) and for reasons related to the gov, cost a little more than e10 91 octane.
I can see station after station only carrying e15 gas and where would that leave us c14 owners? When I’m out slabbing 12 hours a day, the last thing I want to do is worry about finding a station with real gas they my bike can run on. Believe it or not, e15 isn’t enough to satisfy big corn; they want everyone to be forced to buy E30!
Alcohol has less energy than gas. There are studies that show a loss of 3-5% hp and mpg with E10 vs pure gas. Alcohol does have higher octane, but when blended with 85 oct gas to get 87, that e10 87 will have less hp and mpg than pure gas. You can get more power out e85 if you modify your motor with large injectors and more compression.