[Mr Gazza]

Unfortunatly worn plates usually tend to cause slip rather than drag.

You could have one or more distorted plates though, which would cause drag.

It could also be notches worn into the basket tending to hang up the plates, not so common on wet clutches as dry though.

Final thought is the oil (assuming you have a wet clutch?).

Super slippy synthetic oils can cause slip if you use the wrong sort and not the specific motorcycle type.
Minging old oil has been known to cause drag though, or too low an oil level....Try an oil change before you buy the plates..Maybe even use some engine flush for the change, pulling the lever in and out whilst the flush is going round.

....After thought.!... I always used to "free" the clutch on my old Triumphs, by holding the lever in and giving it a couple of kicks until the kick start went down with no resitsance.

You could probably do the same, but with the starter?