What was your jetting before? What was the outdoor temperature? What other modifications have you made to the bike? It does require leaner jetting than before the RAD valve was installed, but some minor adjustments may also need to be made to fine tune things (like raising of the needle slightly). I have a RAD valve and it definitely is an improvement over stock. BTW, just to make sure I've got this straight, did you raise the needle (lower the clip = richer) or did you lower the needle (raise the clip = leaner)?