Loud noises Kirby G 2000

Hello there,

I have a Kirby G 2000, it has been in use for quite some time now. I swapped the motor two or three years ago and everything worked fine, but now the vacuum has become absurdly loud. I know barely anything about motors, I disassembled it and couldn't find anything that looked damaged. I only noticed the carbon brushes sparking quite a bit, but swapping them out didn't change anything. I would guess that the motor somehow doesn't get enough "resistance" anymore, which makes it spin quicker, which then also caused the loud noises and the sparking, but I really don't know how to troubleshoot this, especially since all the parts looked good and were in the right place!
Also: the noise and sparking exacerbates when I connect the hose.

Any ideas or tips how I could find what's wrong?

I will assume here that you know the suction path is clear of debris....only asking since your comment about the hose making worse is a bit unusual.  I recall my mother's old Kirby upright in my childhood home.  Every now and then one needed to check the rotary brush for smooth rotation--if something was jammed in the bearings, either the entire brush needed replacing or some piece of string or debris needed to be cleared.  We also needed to change out the belt from the motor to the brush rotor occasionally.  If yours has a belt drive system, how does the motor sound when all belts are removed?  If the motor still is noisy, it may be that you need to take that to an electric motor repair place and see what they can do.  Good luck!