Worth posting this photo a second time for the do it yourselfers and in the future, when people want to remove/replace the fuel pump. This is the o-ring that it is all about:
Romney Cycles said that 7 of 8 they have looked at have been installed incorrectly. It is
extremely easy to miss how the black ring needs to be installed for both twist and getting the little tabs in place at the same time. The original ring just wanted to pop out of place. Since Yam is doing this for free, it's worth letting them do.