Linhof Heavy Duty leveling head - Repair?

I have a Linhof leveling head with 90mm base. I think it is from the 1950's or 1960's. The clamping mechanism works great when the head is at an angle and will support the heavy Kardan-Master TL. However when used at the horizontal level, i.e. not tilting, it will not clamp tight enough because the clamping lever comes to the end of it's travel before being completely effective. Is there a simple fix to this. I tried getting around the problem by tilting the camera base but the 4x10 back I have will not rotate back to vertical.

Precision Camera in Niles, IL

I had a similar problem, I cannot attempt to give you instruction but I removed the leather from the top and base revealing three screws on each, I removed the top and bottom and 'played around' with tension and lubricants till I got it right, nothing very complicated, cost nothing, has worked perfectly ever since.

Best wishes.