I've just refitted new pistons and rings into freshly honed and thoroughly cleaned cylinders , having checked all end gaps and spacing are OK. I very lightly oiled the rings & pistons before installation and they all went in perfectly, after a bit of faffing. On rotating the crank I can hear a 'rubbing' sound as the pistons move through the bores. Is this normal? I was perhaps naïvely expecting a nice smooth, silent rotation. There's also now some very light vertical discolouration marks in the bores, visible in the residual oil film left above the pistons after the rotation. Do these perhaps mark the piston ring gap position? Should I dismantle, check and re-fit the rings? Your advice would be greatly appreciated. Thanks.