Kenneth wrote:

Hi Vic,

Yes, it is the upper bag that needs to be cleaned... (The
lower bag just contains the stuff that falls so it is not
directly related to changes in efficiency.)

I don't know any fancy way to clean the upper bag, but a
shop vac certainly would not hurt, and others may suggest
better methods.

All the best,

I take my upper back outside, turn the bag inside out and shake the dust
out. Make sure you're up wind from the bag.

--
Jack Novak
Buffalo, NY - USA