Hi
I have a machine with the same problem Model No A701A Ser No A2376417.
I believe that I have found the answer .
If you remove the top cover (as you have already ) and view the nylon drive wheels and drive belt you will find that the larger (driven) wheel has an alloy “dog clutch” with copper coloured spring underneath it. This alloy retainer is threaded to the upper part of a pinion gear which goes into the gearbox. I believe that you will find that the thread of this alloy retainer is stripped. Kenwood no longer supply these parts. I have just spoken to Master spares on 023 8084 4338 who can supply pinion shaft gear and retaining alloy dog clutch (USED) for £11.95.. I guess that it would be best to fit all parts (will involve stripping out gearbox) or you may be lucky and if tread on existing steel pinion shaft is good , only fit alloy bit (can be fitted with out strip out of gearbox)
Good luck
Maurice
Maurice
May 2008