John is very correct, John is "ALWAYS" correct
, about 13.2:1 max. being the average used with 93 octane (pump gas).
The optimum compression ratio "should" be determined by the fuel you're planning to run. Taking all of the following factors into consideration; The fuels availability and practicality, it's average octane rating, it's average detonation rating.
93 octane seems to be the best choice for street use if you are planning on riding it most anywhere.