KitchenAid K5SS Heavy Duty Commercial Stand Mixer "rrk90 parts" Questions

RRK90 Just discovered what the two Rs mean. My wife's mixer slowed down out of the blue. I found a tuning procedure on YouTube and that has it working properly again. I'm wondering why periodic tuning

RRK90 I just found out the RR is the number of times returned to factory. So that leaves me with a PN of K90, however I cannot find the model K90 anywhere on the net. Is it actually a KSM90? Also, the

I am looking for a part for my kitchen aid model #RRK90 serial # wm2813048 and Rpr 000721052 ultra power I need knob or leaver and how old is it ... Write toa main office in the yellow pages for ...