This subject is a regular message-board poser. Many of us have touted our preferences and discoveries whilst playing about over the years. One problem with trying to deal with it on the message board is the sheer volume of information offered and available against the time available to post it.
Even though the SU carburetter (carb) is a very basic yet precise instrument, some fundamental understanding on just how it works is needed to be able to deal with common problems and tuning. Following is as basic a description of what's going on that I can manage!