Hi space age vacuum people! 
I am usually on the vintage thread but I need your guidance. I am rebuilding for a friend a Kenmore upright vacuum cleaner that is manufactured by Panasonic for Sears/Kenmore. The machine has a rotating brush device that turns and in so doing removes dust as it is "bagged" in the cyclonic mechanism. The problem I am having is that the cyclonic brush will not rotate freely, but instead it rotates, speeds up, and then goes "clunk" and stops briefly and starts turning again. I have cleaned the foam sponge secondary filter I am guessing, and there seems to be adequate suction. Can someone walk me through this or have ideas pertaining to it. The machine is from the late nineties I am told.
Thank you!
Nina
