The rubber chunk could be fuel line disintegrating somewhere or gunk from the carbs previous owner still in the entry or other passages. Compressed air, carb cleaner, etc to blow everything out is rarely a bad idea.
One of the nice things about an electric pump is that you get to find out if the floats are sticking before turning the engine over... Also easier starting after it sits a few days (at least with an eddy carb in my experience).
Check your oil for a gas smell or over filling before cranking it though. If it flooded that bad, the oil can get diluted and that can cost extra.
