You can narrow down the source of the noise by using a long screwdriver with a wooden handle to your ear as a stethoscope.
Wild West Steampunk-ish chain mechanical noise is usually normal. Rythmic low pitched knocking or higher pitched rapping is not. Swinging by your local V-twin shop for them to take a listen might be worth some peace of mind. Hopefully they are even slightly familiar with Buell to know how loud they can be.