Jim from creative engineering did a post on that if you take the clutch cable mount off/ out of the engine you can access that slotted spring retainer hold the blade of the screw driver in one of the slots and crank the gear shaft on the rear sprocket side to the right to put more pressure on the spring if I remember right shouldn't take much to make it loaded up more on pressure all of the screws nut etc on these engines are right hand threads at least the one I've worked on are that way.
I could do a picture how to might be a good idea I'll see what I can do.
Norman
Pablo per your request I'm got the pictures now I need to do the posts.
How to adjust your real clutch spring with out taking the engine apart.
