Hello Ralph,
if I have any S.U. problems the first thing I do is to remove the dashpots and pistons, once done I can see where the jet top(s) is. It should be about 1\8" or fractionally less, now with the ignition on (or crank a car with a mechanical fuel pump) I can check for fuel level which should be visible near the top of the jet. If it overflows the float level is too high or the needle valve is passing. Conversely too low or a fuel supply problem\blockage.
After that I check that the needle is correctly fitted in the piston, (shoulder flush with the bottom) and the piston is free in the dashpot. Reassemble and lift the piston which should then fall with a click. If not, then the jet requires centering.
If that is all pretty much OK, look to your ignition. The car will run with quite coarse settings, which then lets you fine tune afterwards.
Reasonable fuel level, jet down in the holder, needle flushish and piston free and it should run.
Alec