Cf70 clutch springs

I've had the bike for about 18 years and the intention was to use the bike as a donor for a ST70 project, anyway it never happened! I gave the bike to my god son who never used it. I now have it back and the plan is to finally restore it!!
When I first got the bike it ran fine and was quite fast for a little thing but after a few miles it suffered from lack of speed. I think at the time i did some research and found that they suffered from a clutch spring problem and that an upgrade was available??? I think I looked at the clutch springs at the time and found that a spring was loose but I'm not sure as it was so long ago!!!
Can anyone please help me???

In these semi clutches, the springs are NOT used to press the plates together.
They OPEN the plates. So reinforcing them won't stop the slipping.

Thicker/ newer / more plates and heavier weights (little cylinders behind the plates, they press the plates together) --> stronger semi clutch.