allright check this out im not sure if this is your problem but here ya go-- a while back i put a master cyl in a vigor. car came back a few thousand miles later and the complaint was clutch slippage. turns out we got a faulty master cylinder and it wasnt letting all of the fluid to return to the resevoir so the clutch wasnt releasing completely (so it didnt have all of its clamping force and it would slip when you stomped on the pedel) now we came to this conclusion by trying to pry the clutch fork back. it wouldnt move. we replaced the master cyl and pry'd (thats not how you spell that) the clutch fork back. problem solved. so you might try that.