Hi Richard, Is there anything stamped on the edge of the mounting flange ? A genuine 289 has a much bigger mixing chamber than a 206/151R. Many components are interchangeable, including the entire float chamber assembly, throttle stop screw, primary air screw, jets, cable adjusters,etc.. BUT, some other items, whilst apparently interchangeable will give you endless problems ! A major culprit is the bottom nut that retains the float chamber banjo to the mixing chamber. Also the hexagonal tube that the main jet screws into is a different length. SO…. You must firstly make sure that you don’t have a mongrel carburettor made up of some wrong items, or you never will get it sorted ! An original 289, as fitted to the 1939 Clubman Special, is 1-3/32″ choke diameter, not 1-3/16″.
Regards,
Brian
