"the adjustment on mine is by the length of the springs,according to the hp of the tractor..i have a 42hp mahindra and the spring length is supposed to be 26.25mm,the more hp you have the shorter the springs should be."
That doesn't sound right to me. It seems to me the clutch should slip, (and save your equipment), or not, (and damage something), regardless of how much horsepower you have, and the spring tension should be determined by the clutch manufacturer. That would be like using a bigger, stronger shear pin, the more horse power you have.