I'm doing my second top end and I'm not sure if I should replace the piston or just the rings. The first time I did a top end there was evidence of major blow-by, a lot of brown areas below the rings and the underside of the crown was brown in color. The piston I just took out looks perfect with the exception of carbon build-up on the crown that I could clean off. I was going to go ahead and replace the piston, pin, bearing and circlips but I don't want to waste money on a new piston if I don't need to. Is there a measurement I could take on the piston or would it be safer to just go ahead and replace it? I use stock pistons in case it makes a difference.
Thanks
DA