those marks are right under the starter motor so you wont be able to see them clearly without removing the starter motor :(

you should have enough adjustment on the cable to get the full travel of the clutch arm anyway.

i didn't notice those marks when i put my motor together as i'd got the later type originally fitted to the original engine.

so try my ignorance is bliss set up as it works fine on my bike.
1.back off the cable adjuster at the lever end of the cable.
2.use the lower cable adjustment to take up all the slack so you have a very small amount of free movement before that clutch actuator lever starts to put pressure on the clutch.
3.now adjust that screw and lock nut on the clutch assembly untill it puts pressure on the clutch lock it off at that position.
4.now back it off a bit on the lower cable adjuster

you should be able to check if its still dragging without re assembling the engine.
if it still drags repeat 3+4 if you get to the stage where you can not back off the tension on the clutch assy with the cable then i'd say the clutch is beyond limits

Thanks for that - it looks like I have sorted it for now. I did pretty much exactly what you said here. Cable adjusters back to the minimum, and then screwed in the clutch centre adjuster until there was a bit of pressure and locked off. Basically I played with the adjuster while operating the clutch lever and watching the plates go in and out. When the first bit of movement on the lever was starting to move the plates, I locked it there. It now works fine, or rather better than before, which was the object of the exercise. There's still a bit of drag, but it looks like the plates are sticking together rather than releasing cleanly, so that may be the reason for that. I can live with it, anyway.

So I took it out for a test ride and ended up pushing it back home for a couple of miles up two very steep hills, but that's a story for another day.

:(:(:(

Thanks to everyone for their ideas and advice.