What brake discs does the Stark have stock front and rear, can I fit a bigger disc, and where to buy one?

Stock front brake disc is 260 mm.

You can fit an oversized 270 mm disc. It needs an adapter that mounts the caliper for the larger disc.

Stock rear is 220 mm; a 240 mm disc can be fitted. The oversized rear disc needs a niceCNC adapter.

Discs and the front adapter are available from Telegram seller @kalina_s_24.