Very few seller are honest to tell the used engine are in good contidion, some time they are showing the engine are running in the movie or in the photo.
The problem are how are the parts in contidion in the inside of the engine when you are looking at the outside of the engine are in nice contidion, see the pic of damaged sleeve. [:'(]
My advice: do not buy the used engine if you are not sure the engine are in good contidion or not worth to repair in case the spareparts are not available. And if you are not a model engine builder with knowledge to repair the used engine.
For the
model engine builders are the used engine not a problem, they will fix the engine with own made engine parts.
See the pic of the engine with my own made parts and look at the engine in the movie:
http://www.youtube.com/watch?v=6jwH6Wc1StY 