65 Chevy, you sure seem to have had monumental bad luck with your O.S. engines. Of the four examples given, I have three of them. The two .46FX's survived my beginner days and are still running strong. The .91FX is one of the early ones and runs fine ( I did upgrade the backplate/ needle valve to the new style). My .61FX was bought used and has never been a problem. I've never owned any of the Chinese engines, so I can't offer an opinion one way or the other. There are some folks here at RCU, who's opinion I respect, who like them fine. The one SuperTigre I own was problem free, just underpowered for the plane it was in. Like Harry Lagman and RaceCity, I've never understood the O.S. bashing that goes on here occasionally. I own 13 of them (two and four stroke), with only bearing problems in a few.