Grab these screen shots on the Solex carb, they go into a lot more detail than Haynes does :
http://www.bxclub.co.uk/forum/viewtopic ... 1&start=84
If you want the original pdf send me a pm with your email address, pdf is just over 1MB.
Also consider a carb recon kit. This is one site I found, referred to in this forum when I did some searches a while back.
http://www.carburetters.co.uk/repairkits.php
I've not called them, if you contact them and they still have repair kits for the Solex carb, price and delivery would be interesting to know.
To answer your question on your carb, from what I remember, it's running lean and the idle speed has been adjusted high to keep it running while the auto-choke warms up. Here are some more links about the auto-choke
http://www.bxclub.co.uk/forum/viewtopic.php?t=1366
http://www.bxclub.co.uk/forum/viewtopic.php?t=1478
http://www.bxclub.co.uk/forum/viewtopic.php?t=3977
IMO the only way you can guarantee fixing it, is to remove it and do a complete overhaul with a recon kit and using that chapter on the Solex.
PS: regarding the socket for plugs, I use an old 5/8 inch, 2½ inch deep, 6-sided socket. Although 5/8" = 15.875 mm, my socket measures a tad over 16mm. If you buy a long-reach 16mm socket I suspect you'll need a 6-sided as well, otherwise the socket walls will be too thick. Otherwise, just ask for a long-reach plug socket
Gap, well on the basis that 0.7mm = 28 thou and 0.8mm = 32 thou, go with 0.7mm
