[XLsior]

There is no roller bearing on a CG250 upper connecting rod. It should be a 16mm opening but these engines can get parts binned...


Unless its a CG200 engine...


I have sanded mine after changing pistons and cylinder of various occasions for various reasons, engine still runs fine.


The piston pivots on the pin separate to the pin in the connecting rod the connection rod moves up and down and rocks back and forth...yes its gets some oil lubrication...But for the most part it is more about removal servicing then operation.


Have you measured both pins? do they look the same...From what I have seen on Aliexpress is there are no 70mm pistons with 15mm pins. The only 67mm piston with a 15mm pin on Aliexpress appears specific to a honda crf 230F application.


Are you 100% sure that the original pin is 15mm OD and that the upper connecting rod opening was not damaged slightly when removing the old piston...



So if you want to get the bike running again without costing a fortune my advice is just carefully sand out the upper connecting rod till the 16mm pin slides in snug. You could smear some copper grease if you're concerned but it will likely wash off with running engine oil...