RE: OS Engine Expert needed....engine
If the glowplug, piston dome, piston skirt.....are all relatively smooth looking and not discolored or "burned" looking.....it should be OK.
If you don't feel and roughness in the crank, and it turns over velvet-smooth, and has good compression....it should be OK.
If it runs well at all stages....it should be OK.
I've owned several engines that have had their "signature" sound. Take the baffle out of the muffler, and run it....then tell us what it sounds like and if the cackling goes away. Otherwise, I'd enjoy that great engine.