Agreeing with Nick here - if the bike didn't need a steering "damper" before you changed the bearings, but needs one now, then the thing you've changed is what you need to sort out.
You have to think about what has caused the change I. The bikes behaviour, and attack that, not something you haven't changed.
Also, your bike's behaviour doesn't sound like any Fazer I've ever heard of. They really don't need dampers unless you've changed the original steering geometry (either deliberately, or accidentally).