I think your use of the term "wobble" may be causing confusion. You stated the PO thoght it was wheel balance. Wheel balance causes a "hop" & the bars will vibrate. It can go away by increasing or decreasing speed. A wobble, or speed wobble, has been well described in the posts above (especially the link by BankerDanny, thanks man!). If the bike does indeed have a wobble & not a hop, keep your speeds down untill it is fixed.