Kirby Ultimate G runs heavy

see if power into cabe use volt meter

this is the Exploded Parts Diagram.

https://www.partswarehouse.com/Kirby-Ultimate-G-Diamond-G7-Upright-Vacuum-Cleaner-s/2818.htm

It is a common fault. There is a video here

https://www.google.com/search?q=how+to+fix+a+kirby+vacuum+neutral+and+drive

..
.

Look at the serial #. Disregard the first number. The next two represent the year, the next two the month, and the next two the day. The last three are the daily sequence.
Example: 5021203456, would be the 456th machine finished on Dec. 3, 2002.

Did you happen to hit the N/D switch by accident on the bottom. The switch has to be in D to run.

Determine if the headlight works before anything else. If the light works but the motor won't you have power thru the vac and the problem is internal possibly motor brushes... or a loose wire on the inside connecting to the switch.
If the light goes out is likely a switch or cord problem. Switches on these vacs break more often than cords. What you see on top is the switch button, not the actually internal switch, however a switch does not normally fail while the vac is running, that sounds more like a loose connection or a bad cord.
So isolate the cord. Unplug it at both ends and plug lamp ( or test meter) into the cord into the cord and gently wiggle where the plug end meets the cord. If the lamp goes on and off the issue is the cord. You can buy a replacement specific to the Kirby series and plug it in yourself. If this s does not isolate the problem, take it to a service center. Kirby is very intricate inside.

Replace the transmission. The tranny that drives these Kirbys can give you problems.

Ok, the hose goes on the front. The light should lift up then, the front emblem rotates. this releases the belt from drive shaft. Underneath where the light was, there will be a release lever, which will release the entire front end where the brushes are located.

Once removed, you will see the intake fan and bar beneath it. The hose hooks to this bar. Then to the left of intake, there is a safety switch. The end of the hose has an arm that will fit into this safety switch.

Once hose is in place, the release lever that loosened the brushes will now tighten the hose.

The bag stays in the same place. If you have the 2nd handle attachment, you can use that to replace the upright handle. The release button on back side of handle.

I own a G4 and used to sell the G6 which was right before the one you own. The G3 thru Ultimate G are work in the same manner just different colors.

Hope this was helpful.

they are pretty easy to use you cant really put it together the "wrong way" they wont fit :-)

No, you just need to take it to a shop for repair.

nuetral/drive, the g series has a power drive motor for the back wheels