HHMM theres an airfield by me and the guy is happy to sell it, I used to by it for my two stroke trials bike, and it ran perfect. Do you know if it can cause any damage to the Harley motor, Maybe the ignition timing would want adjusting, I dont know, but would love to give it a go, I might try a drop in my 883.
No it wouldn't damage the engine, but if it has EFI you could potentially ruin the O2 sensors because of the lead content. Most common if not all avgas these days is 100LL meaning 100 octane low lead gasoline and it is blue in color.
And Jack is right, they run like a scalded dog!