I had to put the big nut on the clutch in a vise and turn the cltuch itself with a strap wrench. it was tough, but it worked.
I tried a Yellow (1500) spring in my Agility 50, and it was too much, I lost a bout 5 miles off the top end that I couldn't get back.
Also, I installed a Open Air filter on my agility and Started jetting with a 98, which I figured would be rich, and burnt up my exhaust valve.
Good luck!
Daniel