did you figure out what the guck in the fuel bowl is? It looks like fuel hose bits. I would replace the fuel line. I just rebuilt a Tecumseh carb. I used a Brigg P/N :398188 needle and seat kit for the seat. I had to replace the tank because it was rusty inside and had blocked the fuel inlet with rust. Luckily the needle was rusted in place and nothing got inside the carb.