Originally Posted by bargainguy

Do you mean the bars are loose within the stem, or that the entire stem mast wiggles laterally as you ride?

If the latter, then it's almost certainly the headset. BF headsets take a lot more pounding because of the tall stem mast design.

I'm a big believer in Chris King headsets on BFs for this reason. They seem to withstand the stresses better than other designs.

If you have a non-CK headset, it must be adjusted perfectly for everything to work well. That's where I'd start.