RE: O.S. .46 AX - bad rear bearing - metal shards... (pic heavy)
Just a tip if you ever find yourself with an engine that has a lightly scored piston or bore.
Mix up a batch of fuel with 25%-30% castor oil.
Run the engine on that fuel and run it *very* lean for a couple of tanks.
Don't let it get so hot that it seizes -- keep the runs fairly short but hot.
You can then switch back to your regular fuel (so long as it also contains at least 2-3% castor).
I've done this a couple of times in the past and what happens is that the castor will form very hard varnish that fills the gouges on both the piston and the bore, promoting a better seal.
There are engines still running (good as new) in our club today after being "rescued" from piston/bore damage in this way.
It may not work every time but it's a *whole* lot cheaper than a new P/L set and there's really nothing to lose by trying it.