Hello Bryan, I have both types of head on my bikes, one with PD slide carbs (CB650C) and the other with CV carbs (CB650SC Nighthawk) and neither have bolt on insulators. Please can you let us know which model has bolt on insulators? They aren't bolt on, on the CB650Z either as they have PD slide carbs as well. They may be off a DOHC 650, I just don't know anything about them.