Hi, I concur with all that's already been said but I'd like to add that I've used a 012 as my firewood saw for 30ish years and in the last few of these years I've been nursing it quite a bit due to similar issues to you.
I don't believe that there's much difference between the two saws except 4cc's and that your 011 may have contact breakers rather than electronic ignition.
about 30 years ago when I bought mine S/H I kind of went through the whole saw apart from splitting the crank which at the time had a little up and down play in the crank as this type of roller bearing has and would have even if replaced..as I've found in other engines... a few thou, but not excessive.
As already mentioned stripping the cases is a bit of a faff, but not terrible, although I'd probably want to replace the bearings of a 45 year old saw along with the seals... but on the other hand if it's done no work, you might get away with it.
Which seal is it that you can't find?
I'm potentially looking at the same job as you and there is the larger 21mm OD seal on ebay from China, I can only find the 19mm OD seal at 3.5mm wide rather than 4... I can't see why that wouldn't work .... Although******!!!??
If you have it wanting to start, which is like mine on cold days, as it is the winter... leave it somewhere warm for a couple of days which may soften hard old seals, take off the tiny air filter cover and squirt a teaspoon of mixture right on top of the reed, it'll be like it's flooded for a couple of pulls and then give you a few seconds of life... repeat several times and you may get life..
Bearing in mind that your carb may be well out of adjustment. so a starting point of 1 1/2 to 2 turns out on L & H may be a good starting point,
Anyway , once you get it to run and get it tuned, if like mine. your problems may evaporate and you'll just need to repeat the process after next winter..
IMO these are great wee un-burstable saws that pull well above their weight because of the reed valve, their noisy they and sing as they rev right out.. old school .. just like me.
good luck.