Max said:The plug has been broken for some time. You can see that the fire was jumping around the crack at the top of the insulator.
There is some agreement on that. Odd that the bike ran for so long with no noticeable affect from the broken plug. I've had the bike for about a year and have had no need to check them up to this point. The bike has about 6800 miles on it.ElrodontheV-Rod said:My first thought on seeing the ground tab still intact that the plug broke possibly to improper installation.Maybe installed w a socket that didn't have the rubber protector.
By the condition of the broken porcelin at the break,it looks like it's been this way for some time.
KVD said:Attached are a couple pictures of the spark plug fragments I was able to retrieve from my front cylinder. I’ve never had a spark plug do this before.