I have a couple of fins broken on the cast iron head of my 1952 Norton ES2. My brother kindly supplied a couple he'd chopped off a scrap barrel he had from his AJS. I was going to have them welded but welding cast iron is a rare skill and my usual welder isn't currently accessible.
So I decided to use JB Weld. Here is the first one:

The worst that can happen is that they fall off. I accept cooling will be compromised but it was running happily without the fins so it won't be much worse than that. They are next to the exhaust port however so I expect will get pretty warm. JB weld is supposed to be good for a constant 500F - say 270C but we will find out eventually.
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