When you get a new/used top tree don't forget to make up some .090" D washers or the same thing will happen again.
When I bought my #$%*box the engine was out of the frame, the guy said the top end had been rebuilt but the engine had never run since, luckily
The front chain slipper was missing along with the two outer Orings under the cam towers. One of the oil jets was broken, 90% of the 6mm threads in the head were stripped, one bolt was an imperial thread jammed in there. Pistons were old with gouges all over the tops of them, hone was very bodgy, old rings in there too, black goop oozing out from the head gasket. Cam chain had been replaced with a rivet link which was buckled. All the valves had been refaced so where they seat was now razor sharp. All sorts of bodgery too much to mention. Luckily the bottom end had not been apart. Top end had been rebuilt