Hi, I want to share my experience, it may be of value as our bikes are from the same era.
I have a 1998 GG TX270, when bleeding the front brake I found that the passage hole from reservoir to piston of the brake master cyl. was not drilled all the way through at the factory.
As the brake pads wore the lever kept moving closer to the handle bar and eventually not applying enough force on the pads to be effective. I assumed air got in the line.
In actuality there was no new fluid coming down from the reservoir to take up the fluid volume of the caliper piston pushout. I disassembled the master cyl. and tried to push a needle through the passage assuming it was just plugged.
With careful inspection looking in the cylinder I could tell there was no passage hole breaking through.
I carefully drilled and deburred a small hole finishing the hole from the factory.
perhaps this could be the issue with your clutch master cyl.
Of course, I had to do this the night before a trials event. It's always that way.
Good luck with yours.
