Should small start-up partners record purchases in initial phase?

Without any financial backing it's on the parters/co-founders to pay for all initial costs of a business (website, product design, production, etc).

If a business hasn't reached an "official state" yet (has not yet been filed as an LLC) should the partners be recording who funded what of the initial startup costs? I'm paying the lion's share right now, and this project would not be able to move without what little funding it has.

Essentially, if I pay for 75% of the initial costs should I be entitled to 75% of the small business that will be created? Or, should I just expect a majority and not such a high %?

You should definitely record all the expenditure everyone is incurring. This is a loan from each of you to the company. No later than the point at which you raise finance...or are profitable...you can agree amongst yourselves what you get in return for this loan.

Yes. Just keep the receipts and write it in a spreadsheet.

Essentially, if I pay for 75% of the initial costs should I be entitled to 75% of the small business that will be created? Or, should I just expect a majority and not such a high %?

Definitely. Although it's hard to tell because you may not have done 75% of the actual work. As well as recording purchases, also record how much time you have spent on certain projects or whatever you are doing. That way, you can sit down when you start to become profitable and clearly see who has put the most into the business and divide shares accordingly.