Rotax 912 ULS - Fretted CrankCase

Call LEAF. They are in the Midwest and do excellent work.

The best bet for a repair on a fretted case is go to South Mississippi Light Aircraft, SMLA..  They do a lot of deep work on the Rotaxes.  There is no repair for a fretted case other than replacement.  The fix from Rotax came back in 2006 with a new case design that changed the way the case was bolted together.  

Call and talk to Ronnie or Morris, I am sure they can help you if you have not already got someone to look at it. 

Cheers