Here in the northeast US, E10 gasoline was mandated as road fuel around 2005, (or maybe '06?) to replace the MTBE used in gasoline to that point after the cancer concerns of MTBE became more broadly understood.
It quickly became apparent that ethanol was hard on carbureted engines. The folks making their living with carbed engines (lawn mowers, chain saws, and the like) were the front line of the learning curve. They started out doing multiple carb rebuilds on their machines annually, then moved on to buying fuel additives, then to using just hi-test E10, (which appeared to remain stable somewhat longer) and finally they settled on transferring any gas in their storage containers older than about 3 weeks to their fuel injected vehicles, which seem up to the task of digesting stale E10 with relative ease.
Because ethanol is both hygroscopic and prone to evaporation of volatiles, what was learned was to purchase fuel only from high volume service stations. The ethanol and gasoline base are mixed together at the supply terminal while being loaded into the tanker that delivers to the service station, and so at that point begins the evaporation of volatiles and absorption of water, an issue here in New England, an environment often described as temperate jungle. Also learned was any E10 home storage must be in air tight containers, and so the vented tanks on our bikes are just wrong for E10 longevity.
So if using fuel containing ethanol, and it's been left in vented bike tanks for any extended length of time, there's a good chance it may have gone off and/or may have absorbed H2O, becoming both less combustible and prone to shellacking small carb orifices.
Best-
George