The manual is not helpful in identifying worn plates and springs. It just says if friction plates are 0.75mm thinner than a new plate and the spring free length is more than 2.5mm shorter than a new spring they should be replaced. Last time I did the clutch I replaced plates and springs. A new friction plate is 4mm thick so should be replaced at less than 3.75mm thick. The free length of a clutch spring is 45mm so replace springs shorter than 42.5mm.
Photo shows a handy tool to lock the clutch. Bolt or weld an old friction plate to a steel plate. Insert this in the clutch drum, take the plates out first Nigel, and apply the rear brake and the clutch is locked up. You need to do this to undo the nut that retains the clutch hub which should be dead tight.
I found the factory clutch hub extractor tool to be the only special tool needed on Trumpys. The clutch needs to be locked up on assembly too.
The clutch hub is mounted on a tapered shaft (the gearbox mainshaft) and located by a woodruff key and held on by a nut and tab washer. There is a tendency for these to come loose, as happened to …… on a Mad Farmers run a few years back. Before tightening this make sure the hub and shaft surfaces are clean and dry.
Then I heat the hub up fit it to the shaft while still hot and tighten the nut to 45 ft.lb. As well as the tab washer, which must be in good nick, I put some Loctite on the threads (not sure why I think I need to do this, belt & braces philosophy?)