Without looking back to the previous thread, I can't recall year/mileage/condition of your bike. Nor can I remember where you live to recommend a good mechanic. You get my point?
Like Ghostbiker says, the rear wheel will spin in neutral on the centrestand as a result of oil drag in the clutch housing and gearbox. Hand or foot on the rear tyre should stop it ... what does yours do?
Bike in gear, clutch lever pulled in (ie, clutch disengaged) you should be able to stop the rear wheel rotation with the rear brake. Can you do this?
If it stops on the brake but spins up rapidly again soon as you take your foot off, the clutch is dragging.
Since your mechanics have correctly adjusted the clutch cable and are certain that the operating lever is working correctly (they
are certain, yes?) then the problem has to lie inside the clutch housing. It could be warped plates, damaged/swollen friction plate inserts, notched clutch basket grooves, the mainshaft end plug previously mentioned or something else.
There's no way of knowing without paying a mechanic for a couple of hours labour to investigate.
Mike
PS. Devilsyam wants to know where you go fishing, that's all ... he hasn't had a bite in months :lol