Hi VC Victa, Well, mate, that throws a new light on it; if there is no other damage than the piston and rings, here's what I'd do.....I would measure the inside of the bore to determine if an original size piston can be used, if so, see if Bruce can source one for you, plus new rings to suit, plus any new gaskets that will be required.
Whilst waiting for them to arrive, de-coke the engine, clean up the head; dismantle and thoroughly clean the carby, check and clean the inside of the fuel tank....there could be heaps of crud in it after sitting for many years.
When your parts arrive, re-assemble, give it a new plug, check for a good spark, fresh fuel, (check for good fuel flow from the tank) and if all is well, fire it up....
I'm sure that grumpy might have further good advice for you when he comes online.
Hoping this helps,
