To save some $$$, do a cross reference to Champion spark plugs at a auto parts place. They make Harleys plugs ,slap HD on them and Harley charges more for them. Some guys like paying $10 or more for plugs, but can't prove they work any better then any other plug.,,
I like the ones that have the right thread for the cylinder head with a white insulator and terminal for the plug wire on one end and a center and side electrode that can be adjusted for proper gap on the other end.
The very best ones are new.
I would use the Harley plugs or go to ngk 6046 iridium plugs, I noticed easier starts with the ngk iridium plugs on a 2007 super glide I had, haven't tried them in my ultra yet.
To save some $$$, do a cross reference to Champion spark plugs at a auto parts place. They make Harleys plugs ,slap HD on them and Harley charges more for them. Some guys like paying $10 or more for plugs, but can't prove they work any better then any other plug.,,
second that. you can pick up a set of champions at your local auto parts store, the same heat range as the OEM ones, they work just fine at about a buck and a half each.