Thanks Deejay. It seems we have a problem in semantics. My apologies. I have understood what you said and have done no damage. The spring pushes the cone away from the engine and hard into the right half of the clutch housing. When the spring is fully extended the cone protrudes as far as possible to the right of the shaft (looking from the front). I get this.
My question is that since it is slipping, should I just replace the cork, or is the spring loosing tension also a common problem and therefore wise to replace the spring while I have it all apart? I hope this makes what I am getting at clearer. Cheers