Thanks Max and AVB,

I replaced the key and tried to start. Now it will actually run very poorly for a few revolutions. Backfiring through the air filter quite often.Compression seems normal now.

Looks like we have damage to the valve train. Is there another key there or is it likely to have jumped a tooth on the can gear? If there is no key and the camshaft gear is damaged not much point going any further. Are they a metal or a fibre gear?
No way getting any of those parts economically.

Probably end up dumping this one
Keep the carby and starter etc perhaps.

Thanks for help
Jeff