Rotational play at the basket means chain snatch with excessive loading of the gearbox sprockets at low revs. If you can easily move the clutch sprocket 1mm by hand, the engine can move it around 4-5mm under load... rubbers are shot and should be replaced.
The rivets should not be simply driven out, this will almost certainly damage the basket and render it useless. Grind off the top of the rivets on the outside and give them a gentle whack so you can remove the steel plate. Push the rivets back outwards and grind the ends down to the alloy pillars of the basket and centre-punch them. Drill down their length with a 4mm drill to a depth of no more than 12mm and carefully drive them out with a slender pin punch. The holes are a bit on the large side for M6 thread, but does work. There is no great tension on the thread. Open the holes in the plate to accept M6x15 hex screws and bolt it all back together after renewing the cush drive rubbers. Do NOT place washers of any kind under the hex heads, the additional height can foul the internal stiffening ribs of the clutch cover. Use medium Loctite to secure the screws.
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