had the same problem with my 04 America...turned out to be easy fix ...the handlebar endcap was making contact with the rubber of the of the twistgrip...this part is affixed with a small phillips screw...I removed it and shimmed it with a small washer to give it a small gap from the rubber on the twistgrip...problem solved! hope this can help you... btw...you might want to use a dab of loctite on this screw when you reinstall it..
