Having watched the video I'd have to say if master cylinder has scratched bore it would be full length going on way bike stalls eventually with lever pulled in fully

Seeing as plates & seals have been changed there really isn't much else I can think of & can't say I've seen this problem before

I had the same problem.. more or less exactly the same problem.

This will be somewhat confusing description, i'm swedish saw your clip on the tube

On your clutch handle you will find a piston forcing inwards the clutch cylinder. that piston have small rubber thingys to make it not dribble all over the floor.

If you remove the assembly and check it for two things.

1) Micro Scratches

2) Bad rubber thingys.

In my case when i pressed the clutch, it would supply force at the beginning, after a while that force would dicipate and the clutch would engage. Thats because air was slipping passed the piston. And the damaged rubber thingys on the piston.

Note, i changed this.. 3 times before it got right.. So i suppose they are easy to damage during assembly also.

My txt 250 has the same problem, alough mine's a 2000/01. I couldn;t figure out for the life of me why the clutch would not bleed. I was getting beyond annoyed. I happend to look down at the master cyclinder one day why pulling on the clutch lever and noticed clutch fluid squiting out it. On closer examination it appears that the chain has jumped forward off the front sprocket and whacked it one, which has resulted in a hair line crack. At