My guess is flywheel too but, and not to sound, silly and obvious? The plug is hot and gapped properly?
Ethanol and small engines as we know them were never meant to be working together. The suggestion to find fuel the engine was made to handle is a good one. You may have to ask around to find ethanol free stuff. If you are anywhere near something like a NASCAR track the guys will know where to get old fashioned petroleum based gas.
Nothing really against Iowans and others growing corn for anything but eating. What a giant, overpriced, paid for with subsidies the Ethanol to fuel industry is. Little engines really do scream for mercy or just fry thanks to the stuff when fed them.
If you get in trouble PM me. A friend, in Iowa, from a farm family with thousands of acres of corn grown for fuel, is really up on the Ethanol and small engine disasters. He makes a small fortune buy John Deere lawn tractors with Ethanol blown engines.