Nothing in a carb can be 'ruined' by Ethanol in gas...
What DOES happen is phase separation of the ethanol, any water that it has absorbed, and the gas...
If you leave ANY gas in a carb in the off season, then you are asking for trouble...
Non-ethanol gas will turn to varnish, and 'ruin' a carb just as easily as ethanol blends...
Ethanol gas will separate, the gas will evaporate, and the leftover looks like gummy bears melted on a hotplate...
To 'fix' the carb, simply disassemble down to the bare casting, and toss the entire parts lot (including the castings, but no rubber or gaskets) into a sonic cleaner...Harbor Freight has one for less than $60...A pretty good 6 liter 'Vevor' brand can be had for $110...
When you reassemble, make sure that you check every tiny orifice in the emulsion tube, main jet, and pilot (idle) jet...Use a wire brush, and just bend one wire over and run it through EVERY hole...Blow everything (passages in castings/jets) out with canned air or a compressor...
Voila...Should run like new...
If you want to avoid all this, simply run the thing out of gas...If you have a shutoff, use it, and let the machine die...
After it dies, turn the choke on and pull it/crank it again...This will suck any remaining fuel out of the bottom of the float bowl...
Take out the plug and dribble in an ounce of 30 weight motor oil, and crank it once or twice and put the plug back in...
Good to go...