I know the piston are +1mm (81), I am afraid the cylinders were overbored causing the larger gap in the piston rings BUT I am hopeful the replacement rings fit better.Use a .003/.004 feeler guage between piston skirt and bore a .003 should be relatively loose. And a.004 should be snug. These feelers are thin enough to flex to the curve of the bore and be fine. Although it will measure a bit tighter due to curve.
The overbore size should be stamped on the top of the Pistons. It will be marked .25,.50....ext
Yeah, I have triple checked everything. Measuring towards the bottom of the cylinder, using the new piston to push it on square. Not over any ports. The ONLY thing I can think of is maybe a shitty set of feeler gauges?Are you using a piston to push the ring in square to a point it's not over any ports. And making your measurements?