@xlr8tion , Peter is right and pretty much a clutch expert
the free play is inside the clutch cover, you will not see it and it is so little you can however feel it if you use your hand down on the actuator arm.
So that being said you will see the arm rotate as you pull the clutch lever. The first little bit of rotation is taking up the free play and then pulls the lifter pie against the pressure plate releasing the spring pressure on the clutch. with pressure released the oil helps the fibers and steels slide by each other.
What your feeling is free play you can not measure it down there only up top like the book states
Now the two nuts on the bottom bracket are for cable sheath length adjustment. Say your cable stretches over time. this would make you start to lose the clutch lever adjuster do to having to unscrew it to take up for the extra stretched cable so you can increase the sheath length to make up for it. This is where you would lengthen the cable sheath and then go back and adjust the free play. I just looked at mine and it is more of a pain with engine guards. But if you need to adjust it pull the three bolts off the radiator cover on the left side (the top one has a brass bushing in it. Once you slip the chrome cover off you will be able to unbolt the chrome screen on the back of the radiator if need to get at the top nut. Usually this is pretty much centered. Now if you want to pull the cable off the clutch actuator arm I found it easier to slacken the cable at the top and then pull the two bolts out of the clutch cover that hold the cable bracket to the engine. Then I slip the cable out of the actuator arm. it will rotate backwards some from the internal return spring. do not worry as it will all line back up. Also the crank arm on at least on our early models has location marks on it. A mark on the arm and the shaft to line it up. This can be off by one spline tooth either way and not affect anything.
Now first I find it hard to check the free play like in the manual above so I just check it at the adjusting fer-rel first with with the clutch lever just sitting there. Note there is no gap between the cable sheath fer-rel and the adjuster Marked below.
the I just adjust the cable slack so I can just grab the gable and pull it out 2-3 mm. Marked below
note that when you do this the clutch actuator arm rotates slightly until it takes up the slack on the lifter piece. You can feel it when it does.
Now I know this is not in the book but I have to admit it was a Triumph Tech that showed it to me
He said it was just easier imagine that.
Now after you confirm proper adjustment if the problem is still there we will move on.
Note not enough free play releases the clutch spring tension on the clutch pack allowing the clutch to slip from reducing the clamping pressure. And as Peter stated above put undue wear on the lifter shaft, lifter piece, and since your is a silver motor the needle thrust bearing on yours. Not to much free pay can make it harder to find the gears (maybe hear the dogs grind as the line up) Also it could be a worn lifter shaft which will not allow the clutch action that pull the clutch open enough kind of like your only pulling the lever half way. This can happen from a few things one being improper adjustment prematurely wears the lifter shaft because there was pressure on it (no Free play) this creates heat burning the lifter shaft like in the picture below good on the left bad/burnt on the right. Also holding the clutch in and revving the nuts off the motor is a great way to screw up a lifter piece and or lifter shaft or both.
Of course we must verify proper adjustment first or in this case the first thing I would do is slacken the cable adjuster at the clutch lever as much as I could so the cable is lose but you do not take it out just make it sloppy once you do this reach down to the clutch actuator arm and move it with your hand. you will see it will only rotate a wee bit in both directions forward actuates the clutch pack (meaning your lifter shaft and lifter piece have no free play or in other words no clearance) the other way backwards you will feel the cut out of the lifter shaft hit the front fact of the lifter piece. Let me know what you feel.
Hope this helps time for a cup of Joe