So I just got a new to us atv for the kids, starts (pull start), runs good.......checked compression 105 psi cold. Put some oil down the spark plug hole and got 125+ psi. Time for new top end. Took it off today everything looks good, no gouges, nice smooth bore. Just trying to figure out if its stock piston/stock bore? It has 5W stamped on the top of piston and I measured the bore and got max measurement of 71.86mm using a cheapy digital caliper. Stock is 72mm bore so I assume 5W is stock polaris piston & size?? What are you guys getting for psi on new motors/top ends? Going to take it to local machine/motor shop and see what they think..........think I can probably get away with hone and stock size piston?