Try adjusting the clutch this way, but first ensure the Clutch lever pivot hole is not worn before adjusting the clutch.
Now,
Screw in the cable adjuster full at the lever end.
Remove the rubber bung on the sprocket cover
Loosen the lock nut with a deep spanner ( it will loosen with a crack and frighten the crap out of you)
Turn the lock nut anti clockwise a full turn
Hold you fingers lightly on the clutch lever
Turn the centre screw clockwise with a good fitting flat screwdriver
You will feel the lever moving out
Keep turning the screw until the lever is about 5 to 6mm from the lever housing.
Tighten the locknut.
Replace the rubber bung
Take the final adjustments at the cable adjuster