My father and I are attempting to rebuild two 1985 BMW K100 Motorcycles. I wish I could get could an excel spreadsheet of parts so I can create an organized set of parts for all parts of the bike.

That's going to be quite a task and I'm doubtful it will reap much reward once you've invested the effort to compile it.  No such parts list exists today except (1) as exploded parts diagrams on online sites like RealOEM and MaxBMW or (2) the BMW SLP program (only available to registered BMW dealerships).  What you might be able to do is spider through the RealOEM site for the model of K-bikes you have and screen-scrape the part number information.

@kyle1352000 wrote:My father and I are attempting to rebuild two 1985 BMW K100 Motorcycles.

Welcome, Kyle. That is an admirable goal.

How about posting some photos of the motos as they are now as soon as you are able. That might take a few preliminary posts first so in the meantime, describe where you found them, how many miles are on them, and your experience in riding and rehabilitation in general.

What you could do is photograph each part in place then off the bike—if it is removed—verify its part number on a parts fiche like Max BMW has, and build a book as you progress. When you have enough posts, look in the Portal's Miscellaneous section at the link First Renovation of a K100.