Well my 660 just got pulled a couple of days ago. There was nothing wrong just wanting a few more mods. It already has a 11:1 piston, Hot Cams stage 1, K&N with pro flow intake, and a full Yoshimura exhaust. The guy that is doing the head work suggested 1mm bigger valves and port work. Any opinions? He says this will really wake it up. I told him I ride trails and dunes mostly.