Gen I or Gen II? A giant hex drive for Gen II, 10mm maybe, will wrench them out. You'll need to tap new 16x2.0? threads into your new bars. The hole is a bit small, needs the proper size drill to get things started right. Or you can go with Gen I bar ends and some split nut inserts. For Gen I there's a company out there that makes heavy brass threaded inserts that then gets the Gen I weights screwed on. Makes for some nice dampening.