If it is a cast iron wheel it should be alright, we ran them on stock appearing at up to 9000 RPM. That is the wheel used on the flathead Blue Wazoom engines. If it is cast aluminum DO NOT USE IT!!! -- Chuck
Ran the 3 hp Briggs cast iron flywheel on Opens for 20 years with no major problems, turned them close to 11,000 rpm at times on G-200 Hondas. It was pretty much the only flywheel to run. We did sling a couple magnets over the years. Charlie sox did have a new one explode on the stand and almost lost a couple fingers. It was always in the back of my mind that they were dangerous, but I wouldn't run one now because there are billet aluminum ones that you pretty much don't have to worry about.