Board Thread:Versus Debates/@comment-28300173-20161104104110/@comment-30530312-20161119193358

Gyuki is simply too big when B does biju transformation. B (human form) may be able to avoid amaterasu using various techniques (even though i doubt he would be able to avoid it for an extended period of time) but his biju is simply too big. Though I admit Itachi couldn't keep amaterasu up for too long either. Plus Sasuke put out amaterasu that time because they wanted to capture B.