I have always had a bad flat spot on my Bis just after the second choke opens in the carb. As I am very near to driving the thing again (just need a a dizzy- please help someone) I would like to hear your opinions on what it is. My assumption is the accelerator pump/diaphram on the carb. When the engine was running a couple of month back I had taken apart and cleaned the carb with compressed air, checked fuel pump pressure, cleaned and gapped points and fited new plugs, timed the engine using a strobe without vacuum advance, then connected it to check ignition advance against data I have to make sure advance was accurate. I also mucked about with the idle mixture of the carb, deliberatly setting it wrong either way to try to force a change of habit with the flat spot. None of these things worked, however there was a noticable boost in performance overall of course as the engine was in poor tune when I bought the car. The car performs very well overall, easily going 70MPH on the flat (and round some roundabouts).
If it is the diaphram, where can i get one from?
