This might be reaching a bit, but as your running out of ideas. Do you reckon that you might have some swarf from cutting/lightening the flywheel which might of entered the one way bearing/sprag clutch causing it to jam tight??
After I cut mine, it was a job & a half to clean with the magnet from swarf.
Also, are you using the same sprag & bearing when you change over flywheels?
Just a thought

Hope you get it sorted
