Valkyries do make a certain amount of noise. It does take some getting used to.
Look at the link below, it takes you to the 'Shop Talk Section, Frequently Asked Questions' and look under the heading 'About Noises'
http://www.rattlebars.com/valkfaq/#NOISEIf you have had the bike for awhile and it has just starting making this noise then it could be something going bad such as a Timing Belt Tensioner Bearing.