1980 t140 clutch?

First thing, is the cable adjusted correctly, do you have some free play at lever end? what do you mean,it doesnt hold at all,Do you mean there is no drive?

 

Yes, need a little more info, is the clutch slipping or dragging, and is the clicking coming from the clutch side or the actuator on the gearbox side?

 

As Camman says there is a ball bearing on the gearbox actuator side that can cause click when clutch pulled in, did on mine.

 

Sounds like it just needs adjusting to push plates off each other when lever pulled in?

 

tighten the cable adjuster at the handlebar end until you have about 3 mm slack if I recall correctly ( been a long time since my Bonnie). Was the bike running and the clutch ok when you bought it, if so what has changed. Or did you buy it like that coz that could be down to lots of things, stretched cable, plates gummed up, wear in the clutch outer.
If the bike has been standing a long time and the adjustment is ok on the clutch,it may just need freeing off . Sometimes you can do that just by holding the front brake on and giving it a few more revs as you declutch and select a gear. Can you go through the gears without engine running or not?

 

Clutch is not disengaging/lifting/freeing off - call it what you will. It's as if you are trying to put it into gear without using the clutch, yes?
Right, now for my memory workout! Pull the clutch lever in and try to kickstart it. That is the usual procedure to free off the clutch plates before the first attempt to start the beastie. Makes selecting first gear much quieter after being stood for a while (overnight?). Also, there is (was) an inspection cover in the primary chaincase, which, when removed, will allow you to see if the clutch is 'lifting' properly when the clutch lever is pulled in.
As Sprintdave says, make sure the clutch cable is properly adjusted.

 

You need to slacken the cable right off at lever, then remove the clutch centre inspection cover, undo the lock cut and screw the centre adjuster in until the plates just start to lift, then back it of 3/4 to 1 turn and re.lock the nut. Then readjust cable at lever as described above, and all should be ok.
If it is still dragging, then clutch springs are probably unevenly set, and you will have to remove primary cover to set them correctly....also as said. it is always a good idea to kick bike with clutch in before starting as they do tend to "stick"...I do it automatically now even if bike is stood for just 30 minutes

 

Meant to add...before you adjust the center, grab the center nut with a pair of pliers and make sure there is no end play. If there is, it could be the clutch inner center nut coming loose and would account for clicking noise....I know because it happened to me
Probably just the plate lift adjuster though...I hope