I have put the bike up for sale for $7,900. I hope it fetches something close to that, but you never know. BringATrailer will only accept it with no reserve, and I'm not much of a gambler.
The last two issues were a slipping clutch and a bad miss at 1/4-1/2 throttle. It has the original Amal Concentric carburetors. Slides and needles wear quickly on those, as does the carb bore. I didn't want to have the widow sink $700+ into new Amal Premiers, which are admittedly vast improvement with all those bits hardened, but a big outlay, so I carefully inspected the carb bores (and gave them a polish), and determined that they may be OK with new slides and slide needles.
An Amal carb guide that I found showed me how to inspect the slides, and importantly pinpointed the exact issue with a worn slide needle causing the 1/4 to 1/2 miss. I had swapped the plug leads (they fire same time, 'wasted' spark as they alternate their ignition timing - no change. So it was the carbs. I got reproduction sllides/needles for both sides, even though the left was the bad missing one. It was about $60. Well, it worked.
Now it starts as easily as my N15, 1 or two kicks for the well-tuned Norton leg, idles at 1K, and pulls strongly through the range with no hiccup. The clutch had been modified incorrectly. It turns out I could put the plates in differently (putting a metal one first against the clutch hub, and removing one friction plate) and reduce the stack height, therefore strengthening the grip from the diaphragm spring. Bingo! Sorry to make your eyes water with such details, but I'm proud of myself.
https://orangecounty.craigslist.org/mcy/d/mission-viejo-1971-norton-commando-750/7851613144.html
There's a whiff of smoke out the left pipe on the overrun as you can see in the video.
It sat a long time. The compression is 187 on each side now, after 100 miles or so, and the smoke has diminished to negligible - but they all smoke a bit. These bikes didn't come with rubber valve seals, but they can be fitted. Maybe they are on this one, I threw some STP in there, and it stopped, so I think so, LOL. My N15CS only has cast iron guides, and there's no smoke at all. I think they are 10K bikes before a refresh.
Not sure why the video never shows a thumbnail, I select 'video' from the toolbar. I'm a feeb.
Now that it's done and running perfectly, I can get back to the Suzuki's blue bodywork, painting, and emblems, remember them? Finally! I'm the worst thread derailer, sorry for the diversion.