I have unsoldered the OEM connectors (uncrimped them first, messy) and then re-used them on new cable. The starters can draw up to 80 amps if you connect the bike to a big (car) battery and the engine is stiff for some reason, which will then burn the contacts inside the starter relay. So, they act as the "fuse" of sorts for the starter cable itself, quickly dropping the current as the copper bar inside the solenoid burns itself.
So, #6 cable is fine in length less than 3 feet. It also will fit back into the [re]used lugs. The stock size from Japan, is directly measured against SAE sizes, is like AWG 6.2 .If you use smaller-strand wire instead of stiff ones, it will also run cooler at all times when used. In many situations this is a great way to improve on a given wire, as having more strands for the size always makes the resistance lower.