I am not sure if it is really rubber but that was the first thing I did was replaced all orings, rubbers, gaskets, and diaphragms. O and gave the carbs a good bath in Chemtool and carb cleaner rinse then blew all passages out with Air hose. Just what I would do but my Diaphragm assemblies were pretty hard with some kind of film on them even had to scrape some of them out with a small screw driver.