I had this problem. It turned out that the Ethanol in the fuel was dissolving the old rubber fuel line . I changed all the rubber lines & the O rings to Ethanol friendly (modern) parts & this fixed this problem LIAM Edinburgh, Scotland
the rubber debris is prob from the o ring that goes around the idle jet stack I made those plugged idle jets problems go away with a big billet fuel filter that actually uses a element that has an aviation part # (I work as a helicopter mechanic) I bought the filter and housing through summit it saves soooo many hassles keep up the good work!
The best way is to remove the air fuel mix screw/s and then remove the idle jet screw/s then flush using small shots of carb spray into the idle jet port. It will flush the path out via the air fuel mix port. They are connected.
This is what’s happening to my splitty it’s popping a lot coughing and spitting on idle and setting off a little hesitant, are they easy to get out? Could I try lower ing the idle jet size,