smythie, like you I haven't heard of Loncin, but they seem to have been making motorcycle engines for a while, and those engines seem to be regarded as serviceable rather than good. Why would you want to replace a Briggs & Stratton Industrial/Commercial engine with an unknown brand that you might not be able to get parts for? If the Briggs is irretrievably shot (say, connecting rod through the crankcase, and no junked crankcase available) it might be sort of understandable, but to describe this move as an "upgrade" seems to be stretching things a bit.
