it is NOT a "well-known" issue. before you start randomly throwing parts at it let me ask you a few questions:
1-do you have the factory service manual for it?
2-have you ever worked on a buell XB?
3-how heavily is it modded? most all are.
4-have you checked your ecm(engine control module/computer) for any stored fault codes?
5-do you have an active or random CEL? acronym for check engine light.
answer above and i'll provide suggestions and solutions.
here's your free #1 if answer is no. http://buellmods.com/