Anyone here know the mechanical differences between the earlier 500 series models (505-512) and the later 500 series. What I am getting at is parts interchange, like fans, brush rolls, and motor parts. Any comments regarding the C series parts interchange with 500 series units would also be welcome.
The simplest thing to do is to match up the old part with the new part. From what I know and what I've seen, the overall fan design really never changed other than the older models had a 6-blade fan and then went to more blades and I cannot recall how many they increased to. The hub on the back of the fan is what to look for, also. All Kirby fan kits come with the same fan but what is different is the metal "hub" and pully that comes with it. The pully will change in length depending on which model you are replacing it on, and the kit may or may not come with a washer that goes behind the pully.
As far as brush rolls go, I always replace the brushroll with the original one. I guess I am a purist. Because what I have seen is a brushroll that has been interchanged with another model usually does not align with the rug plate because the brush pattern is different. A tuft will get in the way of one or more of the rug plate guard bars. Therefore, I replace the brushroll with the correct one for that model. Kirby also owns CWP, Cleveland Wood Products, which is now the grey colored brushrolls which were the trademark of the Kirby. But now they have improved the quality and use a natural wood (I am not sure what kind of wood is used) for their brushrolls now. I prefer to use the ball bearing (denoted as BB in the description) ones since they are quieter and much smoother operating. The sleeve bearing ones are good also but they tend to not last as long.