So, several things. Rec90 is ethanol free 90 octane gasoline. The carb is still malfunctioning due to contaminants. Clean the tank, replace the fuel lines, filter, and clean the carb again. Verify that you have any mixture screws within the BandS specs.
I use an Oregon in-line spark tester to check the spark system. Look at the plug for the obvious issues. If the light is strong, compare to a well-running engine. If not, clean the flywheel and gap the opening to BandS specs. I would start with these items.
Hope this helps, make it purr, I’m sure I’ve forgotten some stuff,
Steve