You might wonder why we do not include big bore high compression pistons for the 750. The answer is simply that the connecting rods don't appear to be up to much additional stress. The material above the rod eye (where the piston pin slides through) is extremely thin and may well streatch and break with the addition of a lot of power. Forty years ago Megacycle Cams offered an 11:1 piston set in .25mm over-size.

The top set is merely a freshening of the 748cc cylinders. I'd guess that most 750 Viragos still running (or able to made to run) won't clean up with a simple hone. The second set cleans up the bores and yields 767cc with a trifle more compression than the stock 9:1. If you plan on either of these routes, consider swapping to 700 heads to boost the compression.