That usually happens when a con-rod breaks, the remaining con-rod attached to the big-end can do a lot of damage as long as the crankshaft is still rotating.
I've invested some cash in a Carrillo conrod to prevent the 'air cooled big end syndrome'...Worth doing if you are intending to really drive an old engine hard...
Looking at the clutch casing could this bike be a Sprinter or Race bike?...Ian