replying to jacobite, Iggy wrote:
There is no adjustment for the fuel/air mix. The Diaphragm or Gasket between the
carburetor and fuel tank needs replacement. When that Gasket deforms it allows
additional fuel to come into the carburetor and makes the engine run very rich.
A tiny bit tedious, but a very quick and easy permanent (as long as the other
one lasted) fix back to like new.