Well, whats that old saying, two out of three ain't bad? I have bought a total of three engines ( two from kits, and one replacement engine only ) from BGF. And the very first one was a total POS turd. It ran for a total of five minutes before the crank bearings went south. Turns out it was the typical " bad " crankshaft that was warped way beyond usefulness. The other two, well I have to say they have been damn near outstanding, considering the money spent. These both are very strong runners, and I have been switching between these two for over 6 months now, and I use my MB for daily transportation, and a commuter. Yes these engines are cheap, yes these engines are all a crap shoot, as well as a pig in a poke. But if ( and most likely ) you get one with a fairly good bottom end. You will get a good service life from them, IF you carefully inspect, reassemble, and maintain them.
That said, these little HT's are not for everyone, certainly not the unwashed masses. But with some care, attention, and TLC. Most should meet with the same success....
Peace, James