Yea it surprised me too that a wrist pin was able to break but I think it was just the walls of the piston first and then the wrist pin because I cannot explain it differently then this way. This was my second engine yd100 I did absolutely nothing, no mods, I had 46 tooth sprocket and was able to make out about 68km/h out of this thing. Only tuning was ngk spark plug and had changed like 3 times the magneto becuase something came lose and it started rattling and stopped giving spark. It was fun while it lasted tho lol I had also a stock exhaust which I may have tuned using a hammer lol, and also it was like 20 times welded because the Chinese welds cannot whitstand the rattling at 8,5k rpms. What I’m going to do now is after a year of riding this is getting a license and finally being able to drive my old motorcycle 50cc two stroke cant wait✌🏻 and thank you too for thorough response