I just removed the belt and turned the pulley back and forth to check for slop in the coupler - not much there - maybe 1/16-1/8". If the noise is the coupler, supposedly it's noisy at idle - not necessarily when under throttle pressure.

If it was the coupler, I could remove the nose drive and replace the coupler, but I'm afraid the noise I'm hearing is the rotors banging together.... perhaps the result of bearing wear. I can feel the banging on top of the blower rotor housing.

I called Magnuson for advice - not much help.... their only suggestion was to send it back for them to see what's making noise. I need to find my date of purchase and see what the warranty is before making a decision to open it up myself.

Frank