Hi Bruce,
I used gasket goo to join the two halves.
I will clean/adjust the carby as suggested.
BTW: I think I know why the engine spat a ring ... The ring pieces that I cleaned out of the exhaust where carbon black and the ring that remained was in the second grove and was steel faced (it had the spring under it as well) ... I think the rings must have been put in the wrong order and this would have caused the carbon black one to flap around (as it had no spring) and catch on the exhaust port ... ??
Cheers
James