I had a pretty bad hole worn in my inner primary starter housing from riding a lowered bike with a 24t front sprocket. I tried patching it myself with some JB Weld and it just wasn't making me feel good. So I sent it to a shovel friendly guy who welded it up like new. Below are photos of my C.O.B. fix followed by photos of the proper fix.
See that crack!?
This is how it is done! Thanks to Jamie for his aluminum welding skills!