Drivetrain Stiff Clutch Cable???????????????????????

I had the same problem, with the same set up as you (UPR 3 hook quadrant, adjustable cable & firewall adjuster.) First, as stated above, get your route right, keeping the cable as straight as possible. I suggest using the 1st hook (closest to the firewall) on the quadrant. You'll have plenty of room for adjutment in the firewall adjuster to make the cable tighter on this hook but you won't have as much room to loosen it if you use one of the other 2 hooks.

Most importantly though, once you've done all that, loosen the cable on the fork, disconnect the cable from the quadrant and pull it all the way through the firewall. Get yourself some oil (I used some gear oil I had on the shelf, as the bottle has a nice little tip on it but you can use motor oil if you like) and while holding the pedal end of the cable up, with the cable as far out of the sleeve as it will go, poor some oil down into the sleeve and work it in there real good by pulling the cable in and out. Keep doing this untill you feel you've gotten the oil throughout the sleeve or untill you can see it dripping from the other end. You'll actually feel it get smoother as you continue. Button her all up an bingo...good to go.

Everyone knocks all these aftermarket cables but as an avid motorcycle rider, I know the importance of a properly lubed cable and these things just NEVER come properly lubricated from the factory. My pedal was so stiff, I damn near had to use the steering wheel as a means of leverage to push it all the way down and while using just the aftermarket cable alone, it actually broke the stock quadrant in less than a 2 mile drive. I did as I stated above and it's now smooth as butter. Actually drove the car barefoot the other day.