Not sure I can see it in that pic. Looks like the case was re-pocketed, maybe that’s why. If it’s just a small crack in a thick part of the case and it doesn’t go through to cause a leak it will be ok for a while longer. If the crack is into the bearing pocket I would think it might spin the bearing when it gets hot.
FAA certified jet engine and aircraft technician,
Nicholson Speedway class champion 2001,
Yamaha KT100 Service Center,
41 years karting experience