need help to pick out the right carb size

im putting a big valve head on my 74 CB125s. dont know if i need to run a bigger carb. the valves are 2.5mm bigger. plan to run with no filter. rest of the motor is stock for now but i am looking for a high compression piston. what size carb do you guys think that i need? aslo what size is stock?
i saw that the ecta record in the 125 four stroke is only 65ish MPH. think that my cafe will do more then that!!! wanted to go and see...so thats why im doin the big valve head and not the bore kit
thanks for any help

There is the right way, the wrong way and the british way to do anything!