TOPIC:

Though you already have all the parts to do the top end right?

Heck I would just start taking it apart.

For me an engine in that condition is only good for rebuild. Rust is incredibly hard and will tear alloy pistons apart very quickly.
Remove the head and barrels and clean it out it is likely to have rust on every steel surface from condensation. With 18K on it the innards will most likely be salvageable but not if you run it.

+1 on what Rick said. Prolly will need an overbore and new pistons. The old rings have undoubtedly corroded grooves in the cylinder walls.

im with Rick on this as well, if its rusted enough to lock the engine then it needs a closer inspection before running.

So I wasn't making any progress, so I pulled the head. Good thing I did.

I am now the proud owner of TWO KZ1300 motors with gakked No. 3 pistons.

The question now is whether I want to send this to a machine shop to get if fixed, or buy a replacement set of bores that are actually in decent shape (that way I won't need to buy an oversize piston and rings, or an entire set of six...)

Time for one of these .
Big bore kit