The ethonal dries out the diaphragm and fuel pump membrane. Walbro actually has released aa spiral diaphragm to help combat this in the smaller wt series carbs, and also offers a ethonal resistant purge bulb. (Silver black in color)Yeah I hear that. I normally run any float-bowl carburetor dry when I'm done using it, especially my '74 RD350. Can't reach the carb drains on that unless you loosen the clamps and twist the carbs in the manifold sideways. A huge PITA to do every single ride. I've found just shutting the fuel off at a predetermined spot from my house, then riding the last 1,000 feet on full choke works well.
As far as diaphragm carbs, I've found leaving them full of fuel results in far less issues. Don't really understand why that is. Maybe since the crap in the gas holds the diaphragm open allowing internal leakage. Not really sure. Whether it's a chainsaw, weedwhacker, leaf blower, or the giant diaphragm carb (Walbro WB-37C) on my paramotor, they will ALL not start the following year if left 100% dry after running E10.
The paramotor sat all fall and winter (After I broke my hand) with E0 & Saber, and fired right up 6 months later. A little extended crank time, but not too bad. The saw sits a year at a time or longer, and always fires up relatively quick on E0. It used to take way too many pulls on E10, usually requiring a sniff of acetone to light off.View attachment 1008683View attachment 1008684
my father in law paramotors as well and has taken a liking to running canned fuel through his motor and fogging it before long term storage. He seems to have little to no issues with his fuel system each spring. It's a neat hobby, but expensive.