I've just written my first mathematical research paper. It proves some new results, which while not ground-breaking are (according to an expert in the field) at least somewhat interesting and surprising. At the moment however, I spend more of the paper developing the background material (giving standard definitions and constructions, proving standard lemmas) than proving the main theorems.
Is this a problem? The way I see it, there are several arguments for and against:
The background material is "standard" in the sense that anyone who works on this class of problems would know the definitions or results in some form. However, this is at most a few hundred people, while if I include the background material my paper should be comprehensible to an advanced undergraduate.
Some of the background results are part of the folklore of the field, and I've never been able to find a proof of them in literature. While they are believable and not hard to prove, I feel someone should bother doing it. More selfishly, this is one more reason for people to cite my paper.
I don't know of any one reference which states all the background material I need, so if I don't include it my readers have to chase down multiple sources and I have to use conflicting notations.
It may be annoying to an expert in the field, although they could skip much of it and mainly refer to the background section for notation.
It makes the paper longer, although even with the background the paper is not long (13 pages).
From what I've heard, it is generally considered bad practice to restate definitions and constructions states elsewhere and to reprove theorems available in literature. In part this is because it gives the impression that I haven't read the literature. This is exacerbated by the fact that I only cite ~5 previous works, mostly for further reading or alternative presentations of some of the background.
I'd like advice on this from someone with experience writing such papers.