This job may be accomplished with the transmission on the bike and the swingarm/tire in place.
I did this work on a /5, however looking at my Haynes manual, there are only a few differences between this and the later models.
First, remove the clutch cable from the clutch lever. The clutch lever that's down on the transmission that is. My Haynes manual suggests slackening the adjustment at the handlebars first. I did not find this to be necessary. I just depressed the lever by hand and slipped the barrel out of the fork prongs on the end of the lever.
Now remove the pivot pin. On my /5, this is held in by a Cotter pin that engages a groove machined into the pin. On other models up to 1980, this pin is held in with a circlip. It's not too obvious from the pictures and drawings quite how this is accomplished, but with the bike in front of you, this shouldn't be too hard to figure out. Feeling nervous yet? Models from 1981 on use a pivot bolt with a nut and a wavy washer.
The '80 and earlier models use a plain bush (machined directly from the aluminum of the lever) to support the lever, while later models use a roller bearing running on a bush.
In either case, remove the lever once the pivot pin/bolt is removed.
On my /5 a small rubber boot came off with the lever. From the looks of the pictures and drawings in the book, the boot is larger on the later models. It also looks as if this boot will remain on the back of the transmission when the lever is removed.
If the boot remained on the transmission, remove it now. The '81 and later models have a clamp holding the boot in place.
Now remove what the book refers to as the "thrust components".
On the '80 and earlier models there are either three or four of these. For later models, read on, they are different enough that I'll cover them separately.
I first pulled out the thrust piston. Mine had a rubber seal, something like a double-lipped O ring in a groove at the center. It looks as if /6 through '80 models might not have this seal. Instead the might have a "sleeve ring" which would come out either first, or perhaps as a piece with the piston. I suspect that this was added at the same time the rubber boot changed. The presence/absence of this part is also why I said "either three or four" a few sentences back.
The piston includes the outer bearing race and contacts the actual ball elements of the bearing.
Next pull out the bearing itself. It's a button sort of deal which is a ball-bearing cage. It transfers the thrust from the non-rotating piston to the rotating components further in.
Now pull out the thrust washer. It is the other bearing race.
The bearing pushes it up against a step on the clutch pushrod (which, by the way, runs through the center of all of the "thrust components").
I had to use a skinny magnet to pull out the thrust washer.
The '81 and later models seem to have been simplified. You should (if I understand the drawings correctly) only have to pull out the piston (with no seal shown) and the actual thrust bearing which seams to contact the step in the pushrod directly.
At this point, the only clutch actuation parts that remain in the transmission are the pushrod and its felt ring (sort of a seal from the looks of it). Well, actually '81 models on don't even seem to have the felt ring.
My Haynes book says that this pushrod can not be removed without first pulling the transmission. It looks to me as if you could pull it out if you were willing to remove the swingarm, but I had no need to remove it, so I didn't try.
Now clean the parts. I used Gunk engine cleaner and a toothbrush, followed by water. I then dried the parts and sprayed them with WD-40 to prevent rusting.
At this point inspect the parts and obtain replacements if needed. I suspect that if you change the actual bearing, you would be best off to replace the piston and thrust washer (where fitted) at the same time. On the older models with the plain bush in the clutch lever, inspect this bush and the pin for wear. I understand that this is a common failure point of this assembly. There is a zirk fitting on my lever so that it may be re-greased in place. Nice feature. It looks as if this disappeared at the same time as the plain bush. I'm just guessing that from the pictures in the book though.
Sadly (since that means that I may have a _lot_ more work to do), my parts were in beautiful condition, so I reinstalled them.
This was one of the few cases where assembly really was the reverse of disassembly. I'll cover it anyway.
First grease the parts.
The place the thrust washer (on pre '81 models) back in. The side with the groove for the bearing balls faces out.
Then put the actual bearing back in.
Now put the piston back in. Be careful not to tear the lip of the seal if you have one.
If you have the sleeve ring on your bike, put it in now. I suspect that you could assemble it to the piston before installing the piston as well.
Now put the rubber boot back on. You may or may not have a clamp. If you have the little boot, install it on the lever, otherwise install it on the transmission.
Now replace the lever. While you are doing this, you'll have to slip the open end of the boot around whatever it wants to grab on your particular model. If you have the later model with the roller bearing and bushing, don't forget to put them back into the lever!
Have the pivot pin/bolt ready as you reinstall the lever. When the lever is in place slide it home to keep the lever in.
Now re-attach the pivot pin/bolt with the cotter pin (use a new one), the circlip, or the nut and wavy washer.
Now put the barrel of the clutch cable back into the fork prongs on the clutch lever. Use a little grease here as well.
If you slackened the adjuster at the handlebars, you'll have to readjust the clutch. Even if you didn't this would be a good time to adjust your clutch.
Reading all of this might make the job sound difficult. Actually it is a rather simple job and, except for cleaning, the actual work took a _lot_ less time than writing this article did.