Then on to sizing piston rings. Clean the bore and lighty lubricate the bore. Using the piston upside down . Push the ring about 1.5 inch down the bore
Using feeler gauges measure the gap
Using the calculations supplied with the pistons. The top ring needs about .04 mm clearance. Basicly if the gap is too big you will loose compression. Fuel can the enter the sump, you won't get proper compression and ignition of the fuel air mix.
If too small then when the rings expand they can hit then squeeze against the wall causing extra friction and heat. That will turn in to seizing the engine.
So I purchased a ring grinder set up
Place the ring on top and give it a few turns on the wheel. Then remeasure . Your better of bit by bit and getting it right. Thats taking to much off and then having to source new rings.
So top ring has to be .04mm 2nd ring .045 and then.oil scraper .04 mm. Its very time consuming.
But keep each set marked to what bore you set them up in. So it will all be purfect.