I've been trying to think of externally-visible differences between the GXV140 and GXV160, and haven't come up with much. However, if you can see the carburetor insulator, that could help. The GXV140 has a thin insulator, almost the same as the GXV120. The GXV160 has a large square intake port, and consequently uses a thick insulator to make the shape transition from the small round carburetor to the large square port. It looks like this:
[Linked Image]

When it comes to getting the machine to work well, the base engine is generally just about as good as the genuine Honda, except for the PCV valve disk which is likely to be garbage but is easily replaced with a Honda one (though you do have to remove the flywheel to do it). The bolt-on bits of the engine are a mixed bag: the carburetors are generally good copies and will probably be satisfactory. The air cleaner and governor plate were not really copied from the Honda ones, and might be anything from just OK to absolutely awful. In the case of the governor plate though, I think you'll find you can bolt on a genuine Honda one from a junk engine. It will only take 5 minutes and is probably the biggest improvement you can possibly make in that amount of time.

In summary, on what I've seen so far, you can make a chonda just about as good as a Honda with very little work, simply by fitting Honda bits in the few places where the chonda bits are of poor design or quality. The base engine seems to last about as well as a genuine Honda. I think I'll be using them myself if I live long enough to wear out my genuine Hondas.