i just can't keep my hands off some of my engine parts.
i have been whittling on g13 flywheels for several years but i just ran my third run and probably final single machine lightened flywheel as well as the next phase machine skeletonized flywheel. the purpose of that experiment was to see just how much i could lighten a factory flywheel without compromising its strength.
this is what i do to lighten a g13 flywheel with material removed from it's perimeter.
the step beyond was to completely remove the material at the perimeter which created windows. removal of that much material required that the starter ring gear was tig welded into place on the back side.
here's a comparison shot.
as always, when you machine a flywheel it breaks the crystallization of the cast steel so it is imperative that you have the friction face surface ground just as you would when having the flywheel serviced prior to installing new clutch components.