Clutch action should not be a gorilla fist requirement. Rigid/Plunger clutch is a sound design, but a few things to check.
The split collar 67 3251 on the mainshaft supports the thrust washer, which to my mind hangs on by its fingernails, the collar groove in the shaft is minimal, even on new shafts. Failure of the split collar or its absence lets the thrust washer run against the oilseal rivets.
Aftermarket clutch rollers can be oversize lengthwise, this will lock up the basket and centre when the mainshaft clutch nut is tightened.
First plain plate into the basket is a thick one to support the spring load against the other plates.
All plates should slide easily in their respective positions, and not all aftermarket plates are made equal. Here a wider manufacturing tolerance is perhaps better. With a stiff action and a groan I'd expect witness marks here and there where components are binding.
Noise from the rotating gearbox with the clutch lever pulled is is likely to be a bad ballrace in the inner gearbox cover, as this is loaded axially as the pushrod is trying to push the clutch and mainshaft towards the driveside.
The main failing with the design is that the basket is poorly supported laterally and even with new components a degree of shake on the chainwheel is expected. They all do that, Sir....
Longstroke assembly of timing covers, magneto, dynamo and front engine plates are a bit of a jigsaw. Assembling the gearbox/engine as a bare unit into the frame is easier, otherwise it's a step forward and three steps back. Trust me.
Swarfy.
