Belt and lifter getting hot right away on start up.

Remove the head from the machine, and unlatch and remove the bottom plate. The brushroll can now be pulled or pryed out. Slide the new belt onto the brushroll and center it. When re-installing the brush, note that one end cap is wider than the other. The brush caps are also marked with 1, 2, or 3 notches to adjust for wear. In normal use, setting 1 should face the carpet. Be SURE both ends are on the same setting. Replace the metal rug plate and turn the belt lifter counterclockwise to stretch the belt into a loop. Place the head back on the machine, latch it firmly in place, and turn the belt lifter clckwise to drop the belt onto the motor shaft.

The belt is not on the motor shaft. Remove the head from the motor unit. With the belt centered on the brushroll, turn the belt lifter a full 3/4 turn counterclockwise to stretch the belt up onto the belt lifter finger. ( Look through the back to be sure the belt is streched into a loop over the finger.) Plce the head back on the motor unit and latch it in place, then turn the belt lifter fully clockwise to drop the belt onto the motor shaft. Be sure the brushroll is correctly installed in the head. Setting # 1 should face the floor.

On this page

http://www.totalvac.com/videos/kirby-vacuum-cleaners-videos.htm

there is a video at the bottom on changing belts on a Kirby

1)First, you turn the square belt lifter on the front of the power nozzle until the red arrows line up (belt off)
2)Remove the power head from the front of the machine. Now turn the belt lifter the other way and line the green arrows up again. This releases the tension on the belt
3)Turn it upside down and release the two clips that hold the metal baseplate on and remove the baseplate.
4)Grab the brushroll and pull it out of the power head. Slide the new belt onto the center of the brushroll. It will hang loose...it doesn't have to stretch around anything yet. MAKE SURE THAT THE BRUSHROLL SPINS FREELY!! If it doesn't, you'll burn all new belts quickly due to the added strain on the belt.

You can get a replacement belt here:

Kirby G5 Replacement Belt

1)First, you turn the square belt lifter on the front of the power nozzle until the red arrows line up (belt off)
2)Remove the power head from the front of the machine. Now turn the belt lifter the other way and line the green arrows up again. This releases the tension on the belt
3)Turn it upside down and release the two clips that hold the metal baseplate on and remove the baseplate and you can access the belt.

You can get a replacement belt here:

Kirby Ultimate G Replacement Belt

Step 1: 
UNPLUG YOUR KIRBY VACUUM CLEANER. Before you go any further, take your time with this belt change. It's not that difficult, just a little different than most other vacuums. These belts are very easy to find on the internet. Step 2: 
You should be facing the front of your Kirby vacuum. The height adjustment lever will be on your right. Push the lever all the way down. Lift the light hood with your left hand. Turn theKirby vacuum belt lifter counter-clockwise with your right hand. Unlock the accessory lock. The accessory lock is located under the light hood. Move the lock to the left to disengage it. Remove the front of the vacuum cleaner.
Step 3: 
Turn the vacuum belt lifter all the way clockwise until the belt drops down. Unlock the roller plate by releasing the two latches on the rear. Pull the roller plate up slightly and then off.  
Step 4: 
Bend one end of the roller bracket just enough to remove the roller. Remove this end of the roller. If you need to replace the roller take it all the way out. Remove any carpet fiber, string, or hair from the roller with a scissor.

Step 5:
After you have removed the old belt, slide the new one back on the middle of the roller. If you're Kirby vacuum cleaner has a belt indicator light, the roller will have a magnet built onto one end of it. It's very important to install to install a roller with a magnet on the same side as the indicator light. The roller actually will only fit into the roller plate one way.
Step 6: 
Place the roller back in the roller bracket. Place the roller bracket back and lock it into place with the 2 latches. Rotate the vacuum cleaner belt lifter counter-clockwise. You should feel the the belt catch. Look inside to make sure the belt is being stretched onto the vacuum belt lifter. Reassemble the machine. After you have reassembled your Kirby, turn the belt lifter cockwise, releasing the vacuum belt onto the vacuum motor shaft.

Vibrating – that usually happens on some short fiber or very dense carpets. When nozzle goes against the carpet fiber Kirby starts jumping. Try vacuuming the same place while facing opposite way.

Belt – red arrows means DISENGAGE. When you install the nozzle on the Kirby unit while green arrows match you will not be able to turn it on red. You must follow sequence (starting from nozzle off the Kirby, green arrows match, Kirby front lifter all the way up by pressing one of the pedals):
1. Turn Kirby knob to match red arrows. You will feel some tension and hook inside of the nozzle is supposed to catch the belt and stretch forming a loop for the Kirby shaft.
2. Put the nozzle on the Kirby and lock it on with the latch.
3. Twist the knob back to match the green arrows. YOU ARE DONE

Go to GoodVac.com Kirby vacuum online manual. There are some small details that you may want to pay attention to if you have removed the brush roll to install a new belt. Also there are some pictures that will help you understanding the process.

Vacuum thoroughly before shampooing for maximum cleaning. Then, remove the bag and the Power Nozzle to prepare for shampooing. Turn the Carpet Shampoo System Nozzle Belt Lifter to the right of the center position (fully clockwise) until the green arrows line up. Slide the slots on the side of the Carpet shampoo system over the outer shoulders of the Carpet Shampoo System Tray. While pushing up on the Belt with your finger, turn the Belt Lifter left (counter- clockwise looking at it from the front) until the red arrows line up. (The Belt Lifter Hook will catch and stretch the belt.)

Press the bottom Toe Touch Pedal all the way down to raise the front of the Kirby.


While sliding the carpet shampoo system Nozzle/Tray Assembly toward the Kirby and over the Motor shaft, connect the hooks on the bottom rear of the nozzle to the Attaching Bar.



Push the nozzle up against the Kirby and turn the Accessory Lock to the
right (clockwise) to lock the nozzle in place. To engage the belt, turn the Belt Lifter
all the way to the right (clockwise) until the green arrows line up. Then lower the Headlight Hood

on the kirby head is a square knob with the kirby name on it. use your finger and pull out the belt and rotate the knob until the metal pawl engages the belt. keep turning until it stops. the belt should be in the correct position to install the head. place the whole head onto the lower two tangs and lift up. now rotate the wedge clamp until it stops. then rotate the belt lifter till the knob is straight.

when you install the hose connector it trips a switch that switches the vac motor into high speed because the vac path is longer using the hose. check the belt after you remove the front. make sure the direction of rotation is in the direction of belt travel stamped in the impeller. try adjusting the head height