I've never been impressed with the materials that Jap engines are made of, where really good stuff is needed, that's what it gets but that general alloy used in crankcases reminds of the old Austin Maestro door handles, high zinc content and the first time it's seriously tested it breaks. It's obviously good enough for what it's intended and for the expected life of the vehicle but I dont think the manufacturers anticipated BOFs like myself trying to keep the things running indefinitely, in my case thirty years. A friend of mine bought a '96 GPZ900 and had the same problem getting the rear engine mounting bolts out.........alloy of sorts vs steel of sorts + moisture............Hell of a job.........heat and measured brute force over several hours worked. The bottom line I suppose is that nothing beats quality materials in the first place but that doesn't make for maximum profit does it ?.
Best to all..............Dick S.