The Harley Hummer Club

Probablu not the cause, but open the groove up where ever there is a burr. No burrs, surface the top and bottom of that ring untill it is free

Im a firm believer in trying the easy stuff first then the hard stuff.
It can’t hurt getting the ring to fit properly then check compression again.
You may need to bore out jug and oversize the piston and rings…. but this is worth a try.