It's quite easy to replace.

You have to remove the clutch pressure plate (the 6 springs). Then undo the clutch center nut. You'll need a clutch holding tool to do this or a good zippy gun.

Once the nut and washer are off the center of the clutch can be pulled out complete with all the plate.

Under this there is a further 6 M7 bolts that hold the clutch basket onto the driven gear. Undo these and pull the basket off.

You can then see the seal. Sometimes if the seal isnt too tight it can be removed without going any further as its only pressed into the cover. If however its tight you will need to remove the right hand side engine cover.
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If I have to take the carbs off once more...