The engine is now mostly back together apart from the carb & starter.
This exhaust collector was a bit too far gone for the aluminium foil cleaning method, it was so rusty I had to use the big wire wheel to start with, followed by lots of sanding with the Dremel to get the gasket surfaces smoother (as best I could), forgot to take a before picture.
I had to make a few more gaskets for the induction & feather valve assemblies.
Here is the coupling used on these UK Champ generators, this one has two three thin washers as the coupling doesn't quite fit level with the PTO shaft.
David