I have made some out of cast iron for a model enthusiast many moons ago. To suit model steam engines and model two-stroke airplane engines.
We sourced the right grade of stock by acquiring an old gigantic piston ring from an engineer friend on a mega ton ocean going freighter.
I cut a piece of it, chucked it up in a center lathe, bored, produced a good surface finish on the OD and face of it.
The trick was parting it off at the exact thickness required and still maintaining an acceptable surface finish.
I ground down the thickness and set off an old hacksaw blade to cut them open with an end gap. The rings were of course produced oversize to provide an expanding sealing tension.
A jewelers vice was used to hold them whist finishing and setting end gap with a flat points file.
We ran the better faced surface finish toward the bottom/lower ring land surfaces.
Quite frankly they worked very well but modern Motorcycle rings are mostly laminated with a variety of plated finishes these days, so that would count my back yard facilities out of that step.
What I would be considering if you are really desperate Topari? is setting the piston up for readily available rings that are close and just simply trimming the piston ring groves to suit.
A hell of a lot quicker and easier.
And is a standard gig throughout the industry, all the way through to extreme performance builds.
