Roller brush not spinning?

The brushroll is held onto that baseplate by the metal brackets on either end of it. You have to slightly bend them outward to remove the brushroll.

the brush bar has 3 settings marked on the end of the plastic clips that hold the bar in place make sure it is set to no 2 both ends,lay machine down and start roll should spin also check bar is free to move by hand

It may have something caught in the roller mechanism if not the belt that drives the roller may have broken or slipped off. If the problem is neither of these then the motor that drives the belt to drive the roller may have failed, Please take to an authorized service centre and have it repaired or replaced if it does not cost more than a new vacuum if it is going to cost more than a new vacuum then discard that machine and purchase a new one. I hope this helps.

The armature that holds the fan on is reverse threaded. It turns to the right to remove it. You can put a nail or nail punch in the hole on the armature and tap it gently to the right. this should loosen it enough to unscrew. There's a washer, then the fan, and a spacer that fit over the shaft.

Remember that the motor will not run unless the vacuum head or hose are properly installed. If this is not the problem, the most likely problem is that the carbon brushes in the motor are badly worn and will need replacement. A less likely problem is that the front safety switch is out of adjustment. While the light is on, remove the head and push the metal rod on the switch next to the fan inward to see if this causes the motor to run.

This might help you - if stuff like this doesn't make much sense to you, then have it professionally serviced for your own safety.
http://home.howstuffworks.com/how-to-repair-small-appliances8.htm

you need to make sure the belt is on the roller correcty, make sure is at the red position when putting the part back on with the belt on the hook, push the pedal to highest (off the ground) position to ensure you put it on correctly, then turn the fixing clip thing to secure it, then once its on turn the panel around to green position, belt will be back on, once you get used to it you'll be ok,

Just got done fixing our Heritage II model 2HD, it had a dirty safety switch. Both the hose attachment and the roller housing depress a plunger to close the switch, thus sending AC to the motor brushes. You might want to try pushing this in and out repeatedly with your thumb, power removed of course, in an attempt to make better contact. If this works to restore power to the motor, it'll be just a short time before the problem repeats itself. You'll have to remove the switch to give it a thorough cleaning. I didn't have any contact cleaner handy, so I wound up using WD40. Hope this helps. Kevin H.

4 possible reasons.
1 – one or both bearings are worn so armature (rotating part) wobbles as it is spinning and cause motor brushes to wear fast. Solution – change bearings too.
2 – Whoever replaced brushes – did not use some brush seating sticks to make cmutator smother and contour brushes to the shape of the comutator (not likely). Solution – appropriately install new set of brushes.
3 – Comutator is so warped that seating sticks do not help anymore – solution – new armature or turn the old armature.
4 – The fact that ONLY ONE brush was worn may mean that there is something wrong with the brush or housing. Maybe it could not move freely within the housing? I think this may be most likely cause it it may be a combination of all 4.Is it worth to fix? Hmm depends how much will it be. If this is 100+ - I’d say get newer Kirby for 300 ad enjoy the tech drive (Heritage does not have tech drive so it is much harder to vacuum with than the newer models)

Here is a online guide....it's for the G series Kirbys. They're similar enough that it should help. Pay special attention to the belt lifting process...it's exactly the same as for the Heritage II, and it's also where I think your problem lies. I have a Heritage II manual available too! Hope I have helped...
Marci

http://reviews.ebay.com/CHANGING-THE-BELT-ON-A-KIRBY-G3-G4-G5-GSIX-ULTIMATE-G_W0QQugidZ10000000003720039