[Walt Fricke]

I've never had an issue. Use an impact wrench. Just be careful you get the Allen fully inserted so you don't round things off.

Or purchase one of the impact tools which look sort of like fat steel screwdriver with a socket for the end pieces to fit into. You operate it by inserting an Allen end piece into the Allen fastener, holding the handle tightly, and whacking the end with a big hammer. This causes the mechanism inside to turn the Allen end piece. And it helps keep the Allen well in the socket. Once started, easy to complete with usual methods.

I suppose you could use heat, but to be effective I think you'd need to apply it to the side of the flywheel next to the bolt you were working on, and that is awfully close to the aluminum of the case. A propane torch can melt aluminum if applied long enough, and you can't count on a glowing color to give you an idea of how hot the aluminum is getting the way you can with steel.