I think I've sorted it out.
It just seems to have been an adjustment thing, but I think a plate or two must have been sticking or jamming somehow when I first started to set up the clutch and that complicated matters.
To recap: I'd got the clutch to work (with the primary cover off) but the nuts on the clutch springs were unscrewed an awful long way. I'd also had trouble with the kickstart sticking, accompanied by a graunching sound, after I'd put the primary cover back and tightened it down.
When I had another think about the clutch and drew a few diagrams to help me understand the relationship between the various different adjusters I decided to approach the problem from the other direction.
The clutch was working and lifting square but the screws were too slack and I couldn't understand why the clutch was still not slipping. Instead of fiddling with the spring tension again, I screwed in the adjuster at the gearbox end half a turn: the clutch then slipped. I then started to screw the springs in 1/4 turn at a time and regularly checked the pressure plate was lifting square, readjusting when necessary. I got the clutch spring nuts screwed back down to almost where the threads were beginning to show and the clutch was still slipping, so I went back to the adjuster at the gearbox end and slackened it of gradually until the clutch stopped slipping. A little bit more tweaking on the spring nuts and a bit of slack put in the cable by adjusting the handlebar lever and we were there: spring nuts down to where they should have been; light lever operation; clutch spins freely on the kickstart when the lever's pulled in. Still haven't road tested it yet but I think I'm there.
Coming to the graunching sound. From one of my photos, Groily noticed there was a spacer missing from where the inner primary cover bolts to the frame at the rear. This spacer pushes the inner cover out at this point. I thought that by adding a spacer here, my problem with the tightening kickstart action and the graunching would be worse because I had convinced myself that something was catching on the inside of the outer primary cover. I thought this because I had discovered a light scoring on the inside of the cover where the clutch rotates.
I thought I'd give the spacer a go though because there should be one anyway. I had noticed that the outer primary cover didn't sit very flat on the inner before tightening and could be rocked maybe 1/4", so I tried adding different thicknesses of washers to where the spacer should sit to try to reduce this. I got the gap down to about 1/8" and left these washers in in place of the spacer on reassembly.
On tightening down the outer primary cover screws and checking kickstart action: nice and free and no graunching sound. I can only think that the primary inner case was catching on the back of the clutch drum somehow and causing the trouble... all would be hidden from view, and that the scoring I had seen on the inside of the outer cover was a historical red herring.
Can anyone tell me the thickness that said spacer should be on a '62 model A10? My inner cover is now spaced out about 5mm in new money.
Thanks for all the help. It led me to sit down and understand exactly how the whole mechanism of the clutch works together, and saved me from sawing a bit off the pushrod...
Regards,
Terry