While I was in the shed doing the carb it was also due for an oil change so it was also time to do the NSU screws. I found them both intact, but the lower one was not much more than finger tight, so some blue Loctite and reassembled.
I acquired a clutch cover gasket just in case, but the original came off clean so its been recycled. The clutch friction plates looked fine, and measured to spec. The steels were somewhat blue, so been hot in the past. Works OK, so until next time.
Like many others have said, check the NSU screws before its too late. NSU aka Neutral Switch Unit under the clutch.