Not familiar with how the bearing is retained. Looking at Bike Bandits website
http://houseofmotorcycles.bikebandit.com/parts/Triumph/AMERICA/All/2290976 it appears that it is only a friction fit. Suggest the bearing be installed with a mild loctite if there are no apparent circlips to hold in place. Usually a needle bearing has an interference fit to its bore. Relys on friction to hold in place. I don't think the outside race to the bearing would have worn out. The bore was probably drilled slightly oversize when made. Try a Loctite that is used for "retaining" such as 609.
