Sad news indeed.

Did you sort out your engine eventually, or did you end up with one and a parts one ?

I never sorted out the 400cc engine, as the replacement I bought was a lemon and I didn't have the time to build one engine out of the two, so I ended up buying a 600cc engine to do the conversion which also stalled due to lack of health, motivation and somewhere to work on it.
Now I have the time and a nice place to work on it, but no money, ha ha, can't win at all.

I think I know somebody who will have the duff 400 engines ... I'll have a chat to them
Drop me a pm to let me know the price and shipping

I stripped the replacement engine and sold a few pieces of it and I haven't seen the original engine for years so I will have to dig it out to check its condition before I try to sell it.
No idea on prices for any of the parts, so will have to check ebay to see what things are selling for nowadays.