Hi,
Hopefilly this may help someone. I've just got an old Kenwood Chef A701A from ebay. It all works but when I was running the whisk attachments it sounded a bit rough. It seems to be fairly standard for the old ones be making a bit of a noise when coming from ebay
After quite a lot of searching around the net I finally found out that this is often caused by a lack of grease or a belt that needs replacing.
To test this - I removed the cover where the blender goes - this turns off the whisk part and it then ran nice a quiet - so issue was likely either the belt or gearbox.
Now luckly not only are parts available via both ebay and partsmaster (There's a 10% code on the MS forum from 2007 that still works) - but they are also VERY Easy to fit.
I have purchased a new belt (about £6 and some food grade grease £9 from ebay - I searched for kenwood grease).
So how to Grease.
1. Open up the mixer as if you were going to change the whisk etc (you know push the button on the side and the whole thing pivots up).
2. Unscrew the 4 screws that you call see on the underneath of where the whist goes into - on mine it's a big blue plate and then the cover will come off. There is a felt filter that may need a clean or replacment. Take that off. - The big grey cover you now see is the gearbox.
3. Find the big penny size screw and undo it - GREASE goes in here if it looks full - don't believe it unless it was serviced - as because the hole is underneath it will collect whatever grease is left in - mine looked full on first inspection. I used a smallish funel and it fitted the hole perfectly - then I slowly added grease over a good few hours (To do this I found it easier to turn the whole unit upside down and prop it up so it doesn't fall over - also I did a one point put the whole unit on it's nose to let the grease get right in - I did that after i'd added about half the grease - with the screw done up) and then put it back on it's back opened up the screw and added more - mine took nearly they whole 100g.
You can try heating the grease to get it in a bit easier -but i left mine at least a few hours for each top up as i was not in a rush.
4. Now put it back together and try it - mine now sounds brilliant !
How to replace the belt.
1. Take of the top as if you were adding a blender - that's the big cover on the top at the back (use the leaver to release it) and remove the cover right on the front (The one that looks a bit like a handle with writing on it - that sits above where the whisks etc go.
2. Unscrew the three screws around the metal ring.
3. Remove the ring and now the top will come off.
4. To replace the belt just turn the belt by holding it near the big wheel and slowly ease it up - near the big wheel - to put on the new one reverse.
5. Then put the cover back on, the ring and the screws etc.
Job down.
Hope this helps someone
Finally I've just had a quick look at the A901 and the KM Series and they seem to have a greasing point on the gearbox - but it looks like a red plastic bung - I assume it's grease as you can buy A901 grease - but I can't confirm this so someone else maybe able to confirm it.