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Yes, increasing the bore without making any other changes will increase the compression ratio.
"Say we have a 500cc single-cylinder engine with a bore of 100mm and a stroke of 63.66mm. Let's also say its cylinder has a combustion chamber volume of, for the sake of easy calculation, 50cc. With the piston at BDC, the total volume of the cylinder is 550cc. With the piston at TDC, the volume is reduced to 50cc. Its compression ratio, therefore, is 550 divided by 50, or 11:1. But if we give the engine a 2mm overbore and make no other modifications, its displacement is now 520cc. Total cylinder volume is up to 570cc, reduced once again to 50cc at TDC. Dividing 570 by 50 gives 11.4:1."