You're likely to do more damage than good that way. Never disassemble an engine more than you need to. Every time you pull out the crank, you have to replace the bearings as they can't handle the side forces you'll put on them.

The best way is to remove all o rings and let them simmer in a crockpot of ethelene glycol antifreeze overnight. Take off the carb, head, and backplate and soak them too. That will take all of the old varnish off and let you get an honest evaluation of the bearings and sleeve. Then replace all the o rings with new ones, which really needs to be done every year or so anyway. A different option that I've used successfully before is to soak them in fuel with the aforementioned items removed and turn the crank and carb barrel a few turns every day to break up the dissolving varnish. When you are done, you'll probably still need to clean the spraybar in the carb. Then it's still good practice to replace o rings, and maybe the backplate gasket.

It's up to you whether the effort is worth it or not, but doing the above will get the engines ready to run, which lets you tell buyers that they do indeed work.