Not all lister flywheels come up like that!
I have a "workhorse" lister L petrol of around 1924 vintage, and sent the flywheels for powder coating.The blasting removed a considerable amount of "Icing" to expose porosity like a sponge cake! The problem was restricted to the spokes but the larger bubbles are still clearly visible after coating. On seeing this I had visions of flywheel explosions (and all that entails!) but I've calmed down a bit now and assume it's OK because :- 1) as far as I understand it,flywheel strength is mainly in the rim, 2) This motor is only rated at 450 RPM, and 3) it's been OK for the last 80 years, so who am I to argue?
It's weird seeing a motor of that age sitting next to my listeroid and knowing that some of the parts are interchangeable.If heaven has engines though,they probably have Lister on the side!
Cheers
Brian