My DR had the commonly over tightened crankshaft nut cover issue. Mine was bad enough that I couldn’t get the plug to move at all before the hex head completely stripped out.
I knew I would have to cut this out. Since my new parts came in today I decided now was the time.
I started by thoroughly cleaning all the oil off the inside of the magneto cover and then covering the coils with masking tape. This was to keep the bulk of the conductive aluminum dust off of the windings.
A standard Dremel heavy duty cutoff wheel (non-reinforced) fits this job perfectly. Using this I cut away at the wall of the plug.
I did not cut through all of the wall because I did not want to damage the case. I cut through about half of the wall thickness then flipped it over and drove punch through from the inside. This cleanly knocked the face of the plug out.
As I suspected once I got the face off the inner threaded part simply unscrewed with my finger.
One last important point. Once you’re done you need to very thoroughly clean the case. Get rid of all of the aluminum dust.
Now you can put it back together and put a new plug in. Don’t over-tighten it, please.