Get your self some air tool oil or some of the commercially available "after run " oil from the hobby shop.It's blended to coat and stick to parts in comes in contact with. On engines with bearings, you want to really lube them up so the oil flows around the balls and races, coats the crank and anything else steel. Some guys put it right down the venturi, then bump the engine with a starter for a few seconds, but if the engine isn't mounted, I wouldn't do that! Once you have things pretty well oiled, wrap it in a good plastic bag, or two. When you run the engines again, flush them with a bit of fuel, then burp them with a few primes down the venturi to run them in short bursts to blow out the oil. Plain bearing engines are pretty much the same deal, but might not need as much oil. Amount of oil is kind of proportional to the size of the engine. If you store them in a tightly sealed box, that will help keep moisture out. You can get all sorts of plastic tubs these days with good sealing lids. If they will be in a damp area like a basement, that would be the best thing, along with some kind of desiccant to help absorb moisture.
   Type at you later,
   Dan McEntee

    Do not use WD 40!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

 
                                                                                                   Frank McCune

     I didn't mention that, but yes DO NOT USE WD_40!!!!. I have seen it etch and attack aluminum over time. Marvel Mystery Oil will get thick and sticky and gum them up also. They do make a Marvel Air Tool Oil  and that is what you want. Even automatic transmission fluid will do if you have no access to anything else. I have seen old spark ignition engines that were oiled well with common non-detergent motor oil (like they used back in the day)  and then bagged up and they looked like new. All oil ain't the same.
   Type at you later,
   Dan McEntee

I use George Aldrich's recommended Rislone Oil Treatment.  They start right up even after decades.  When you store your engines in the fall you really don't know when you will run the next.

I hope the Cosmoline bath was tongue in cheek

I had the misfortune on being in a crap "detail" once in the Army.  We 4 sad sacks were to put 2 dozen well preserved M14s from early Viet Nam back into service and I can say with absolute certainty it is a great preservative; I never want to smell or touch again

What is the ideal way to prepare an engine that will be stored away for many years? I have some older and newer engines that won't be used for quite a while. The engine sizes vary from .049 to .90's.

Two part process really.

Firstly remove anything form the local environment that can do damage like oxygen and humidity (vacuum bag it would be the best like they do with food products),  remove any unburnt or residual chemicals (I prefer flushing with kerosene before oiling) and secondly ensure that it stays the closest to the condition that you left it in by slowing down the aging process.

You are never going to stop rust and rot completely but a good layer of something like an aerosol battery terminal preservative has served me well over the years.
Spray in into the inlet and exhaust, rotate to cover every internal surface, and here the residual kerosene helps to reduce the viscosity and further coat hard to get to nooks and crannies.

Double zip lock bagging is good but vacuum/heat seal packing has to be the ultimate and many household kitchens have that under the cupboards already.

Cheers.