I assume you've still got the Stromberg on there.

There are some tiny parts underneath the dome on the side with the two coolant hoses.

There is also a pull-up diaphragm under the triangular plate facing upwards that interacts with these little parts in the start-up enrichment circuit. I seem to recall that these little parts can get a bit sticky in there and that this can result in an extremely rich mixture persisting.

There is a kind of ring gasket for the dome, but you may be able to access the starting circuit parts without removing the dome by removing the three screws that hold the dome and another piece on the starting circuit, but access to the screws might not be very good. You'll probably want to remove the cooling lines to the dome.