<----That blew a plug out riding around Daytona a couple of years ago (when the pic was taken), but apparently nothing wrong with the threads, Must have shook loose, is all I can think. I got the plug wrench out of the tool kit, along with a pliers to reinsert the hot plug and screwed it back in. When I get around to pulling the head for a new head gasket, I'll check by threading a plug in from underneath.
I still have a small box of helicoils I used to put in Britbikes with knackered plug threads, but never had to use one in my own. If the need were to arise, I'd avoid using them and instead employ a Time-Sert or something similar. Much more secure than a glorified spring.