I also have gotten several engines off E-bay the one used one happens to be "used" a little too much and I am sending it in for a check up.
the cost of a new cylinder and some new rubber O rings and any savings just got flushed down the toilet.
the new engines I have gotten have been as advertised and run great,and have been at good prices, I like to be able to break in my own so I know there hasn't been that one lean burn in run that kills it .