This year testing day for the MGB roadster came with abysmal weather. The only positive about this was that we could test the soft top and find that it was mostly waterproof.
Of course the emissions problem needed to be corrected as soon as possible. We soon found out that the spring(under the slightly rusty part) at the spindle that pushes the jet up was not tight enough. that caused the jet (the black thing in this picture)to move up and down a little, causing the mixture to go rich or lean accordingly. This is a picture of a spare unit I used for reference
The spring looked a bit wonky, so I took the nut off and spilled a few parts on the floor, but careful reassembly seemed to fix the problem.fitted an SU HS6 from an Austin 1800. The 1800 air filter just clears the master cyinder, but this setup works well.