exactly the same thing happend to me, can i ask what else you had to do to put the mk 2 engine in ~? i can get a hold of a mk 2 engine but dont know what else i will have to change

recently my sprocket came off and has put a hole in my crankcase .. so i am after a new engine ........................ or any ideas on how to fix ? there is a chunk out of it 2cm by 3cm