I have ran into this on bikes after they sat for a while. Also when it was really cold and the bike had "summer weight" oil in it. Extra strong, pressure plate, springs don't help either.
Sometimes putting the bike in gear, pulling in the lever and rocking it back and forth really hard will work. I hate to jackhammer the internal chains. But At least is less time than tearing into the engine.
I hate it when any bike WHACKS into first gear. Having a wet-clutch stick on a cold motor is nothing new but I just have to try to work around it as best I can.
I had one that was particularly pron to stick in the morns.. So I devised a cold-start ritual:
Pull in the lever, place it in 1st gear and hit the starter. I allow it run it into a wall while the elect starter is turning. LOLLOLLOL That sounds sooooo freekin stupid but it works on ones that only stick on cold mornings. About a foot of roll will do.
Barring all the easy stuff...If all the mechanicals look to be working then the plates are simple "gooed" together. So I open the clutch basket and remove all the plates, wash them and reassemble.
Some combination of the above has always worked. And please, stop laughing at me Mates
