750 piston clearence

On my '72 Combat the original pistons' ring grooves were incredibly worn out but the cylinder bores were still OK. I replaced my pistons (keeping standard bore) with the newer type Hepolites around 25K miles. Looked again at 35K miles and both pistons and bores all OK.

To measure cylinder wear accurately you need a clock type bore gauge, which will quickly indicate taper or and ovality. If the cylinder is worn out of spec, its pointless fitting new rings or pistons, and a rebore and new pistons is the only proper remedy.

Tricky to measure with the expensive gauges, so rarely needed by home builders. I take my barrels to good shop that does this all the time so they can mic it out and report the score to judge next step. For hone, about any shop will do, but for re bore I'd send mine to a Nortoneer with a torque block set up. Best if you send pistons too to get gap in right ball park.