It can be viewed as short for 你問我喜欢吗？我是喜欢的。(If you ask me if I like, I would say yes.)
That implies the speaker don't want others to notice the fact as the speaker answers yes only when asked by others (i.e. not so willing to answer). So in your sentence,
保龄球喜欢是喜欢，但我打得不好。 ==> Yes indeed I like it, but then I don't play well.
Since I don't play well, I may be reluctant to say I like bowling, as it is not good to know that (E.g. Will the listener look me down when he know I like playing bowling but do not play well? It is awkward to say that.)
That's why using the pattern "X是X" is usually followed by "but".