I have used ethanol on one Briggs-Stratten engine and methanol on several 100, 250 and, 360 cc motorcycle engines. ALL required major mods to fuel flow and carb jetting. On the Briggs I used a remote fuel tank and larger fuel hose with a 7/8" Dellorto and adjustable main jet. No problems at all.
Methanol required flushing the fuel system, but ethanol did not give any problems between uses.
Almost forgot, I did boost the CR and advance the ign. timing on all.
Rod