Draganfly don’t have any but another enthusiast has come to the rescue!
Problem solved.

Where should I go for some +40 Hepolite / Alcan piston rings?

Maybe locktite has been used on the centre bearing but there are two stages to separating the crank halves from each other. Firstly by taking the tension off the cap head and secondly continuing to unscrew it until resistance it felt once again when the tapers can be forced apart. If you have done b...

There is a drawing I could look out if that would help you?

Richard
Suggest that, after inspection, you put it back together and get accustomed to a little piston slap at tickover. If it runs okay, it’s unlikely to lead to any failure and, if it’s intolerable, easy to lift off the barrel off for rebore at a later stage.

Ivor

Have you considered piston slap as the source of the clatter? It’s very common to have some level of piston slap on these engines and would seem to fit the description you gave.
Ivor

Ah, so what you need to do is fit a clear plastic tube to the projecting pilot jet after removal of the pilot jet cover nut. The height of fuel in the tube should be seen to match with the pip on the cover.

Hi Paul
I assume you know that the ‘pip’ protruding from the float bowl cover is the correct fuel level and you should be adjusting to suit?

You can buy platewheel sprockets of the size you want to fit to an old cast iron carrier which can then be either bolted or welded together.

Glad to hear your sorted out now, well done for preserving

So am I correct in thinking that in summary, you got the cylinder pressure up to 100psi and it still wouldn’t start but then fitted the new carb and hey presto!