Begin with soaking the fibrous friction plate discs in clean engine oil for at least six hours, better leave overnight.
Drain the engine oil, clean any loose dirt off the clutch cover, remove the clutch cable and cable holder if necessary. Undo the bolts of the clutch cover in a criss-cross way.Take out bolts and store them safely. Usually the clutch cover is stuck, loosen it with light hammer taps. Only use a hammer with a plastic head or a hard rubber head for this. Do not try squeezing the cover away by driving a screwdriver between the two surfaces. This will only result in oil leaks later on.
Once the cover is off use a scraper to clean the two mating surfaces and get rid of any gasket material that still sticks on. Take your time and be thorough here, it is worth the effort and will save you hassle later on.
Now it is time to take the pressure plate off, usually held by five or six bolts, depending on the bike.
Take the bolts out, together with the springs.
Replace the springs, they are cheap in comparison to the rest that you are going to purchase for this repair job.
If the clutch is knackered, the springs are usually knackered as well.
Take off the pressure plate, take good note of the order the plates are stacked in.
The very last fibre disc is usually thinner than the others to allow a pressure ring to fit, but not always, depending on the bike.
Now its time to check the metal discs as well. If they are warped, discoloured or show any other physical signs of damage, they will have to be replaced as well. If they look ok, measure the thickness of them with a digital vernier caliper. You should get the information from any decent repair manual.
Usually the metal discs outlast the fibre discs, but that also depends on the individual riding style, most and foremost.
Once you are happy with everything and decided what you want to replace and allowed enough time to let the fibre discs to soak it is time to put everything together in exact reverse order.
Do not overtighten the spring bolts, they only require between 10 to 16 NM each, again, depending on the bike. This is nothing, if you are not familiar with this load I would recommend a torque setting.
Always use a new clutch cover gasket, even if you somehow managed to “rescue” the old one.
Always use a gasket compound like Hylomar with this as well to make sure there are no oil leaks later on.
Refill with new engine oil, reconnect the clutch cable and adjust if necessary.
Enjoy your new clutch.