I know where a complete, running, 84-85, 125, with a disappointed owner, is. My buddy had the cylinder rebuilt only to find the seals were bad too. Should have been obvious, but he doesn't want to spend any more on it. Maybe 20 mins on cylinder and piston. That was while he tried to fix the smoke bomb effect of the seals. I'm sure he'd part with the whole bike cheaply or trade for KDX 200 bike or KDX 200 engine. Are you close to Indiana?
The bike is all there, but plenty of things need replaced like tires and levers, but with, like mentioned, a motivated sellar. Its not a 250, but maybe lots of parts are interchangeable, I don't know.
It had Olihn Shock and a DG Pipe, if I remember correctly.