Back to the bike again today, with my trusty sidekick, BayChimp, for added enthusiasm.
I was tinkering with the exhaust baffles when he arrived at the garage, so I left him to remove the engine casing & fit the replacement clutch centre, (from an early model XS). As we had 2 sets of clutch plates, we decided to go with the older option of 7 friction & 6 steel, so used the newer ones, plus one of each taken from the Ebay clutch & put into the middle of the pack. We backed off the adjusting screw on the pushrod & slackened the cable, then re-set it all.
Result- we appear to have a working clutch, though we're being cautious about celebrating until the engine's running again & we can properly check it. Think it still needs some cable adjustment, but with the back wheel off the ground & in 3rd gear, the wheel spins with the clutch in & turns the engine over with the clutch out -so seems to be doing what it should. Hurrah -maybe.
The lever still feels a little stiff, but it's a long time since I've ridden an XS & I can't remember how they felt. It may ease off with some use or adjustment. Absolutely no reason why the other clutch didn't work, but it just didn't.