Apology for hijacking your post, however, I am also looking for an auto advance / retard unit, only for a '51KH500, Fieldmaster, see picture. Pete, much appreciated if you will have a look through your spares.
MY KH autoadvance was the worst of the two I had.
It's pretty sticky at least and the state of the taper is unknown (I have no mage to try it on).
It was effectively a "spare" should I ever require bits
If yours is in better nick, Pete, then it;s likely wider wiser for him to buy that.
South Africa is a long way...
John Nash
AOMCC No.4119
''78 t140 bonneville, '77 BMW R80, '67 CJ750, 196-ish Ural M62 outfit, '51 VH500, '49 project Ariel , '47 VH twinport, '44 Ariel WNG, '42 indian 741b, '41 Ariel WNG and piles of rusty scrap ....