Has anyone used this stuff? Just might help smooth out thumpy.
http://www.barbuzzkill.com/default.asp?sec_id=180003901

Before you buy this to put in your stock handlebars - you should be aware that the stock handlebars have steel weights welded into the ends.  These weights are solid and don't have a hole in the end - so unless you drill a hole in the center of the weight you won't be able to install anything in the handlebars.  The weights is really long - it would not be easy to drill all the way through it.