Hi.
I think the chap you need might be me.
I specialise in the repair and service of honde generators and have done for over 20 years.
Is the fly wheel intact.....are there magnets missing from it and is it distorted?, trouble is that if a magnet is cracked or dislodged you will not get the generator running as it should. To rum with one magnet missing will make the flywheel unbalanced, either way you need a new fly wheel.
You can contact me *LINK REMOVED* I have lots of used parts too so will be able to get your EU20i up and running at a reasonable price.