Thanks Art,
You are also a very knowledgable guy too...... I have not got the expertise or facilities to investigate or verify either of your diagnosis. Either way, it strongly looked like an engine strip down of the top end. Fixable yes.... but not by me, and expert time, labour and tools cost dearly. Was sad to see the CBF-F go, but I'm also delighted with the NC750X. Serviced correctly and regularly, I've seen evidence of NC's doing North of 250k km.
You may like to check out mototuning.ie. If they don't know what they are at, then I don't know who does?
Value your thoughts as always Art. The Internet would be a barren place without helpful people such as yourself 👍👍😊
Stay Safe man.....
Niall...