What would cause inadequate clutch release?

Inadequate clutch release can be caused by many problems. Possible causes may be as follows: Clutch linkage not properly adjusted or reset. Flywheel not resurfaced before new clutch installed. Flywheel surfaced improperly (I.E. Incorrect flywheel step). Flywheel machined too thin or not manufactured to stock (O.E.M.) specifications. Lack of lubrication on linkage or release bearing collar. Linkage worn or damaged. Hydraulics defective, leaking or air in the system. Cable stretched or damaged. Pilot bushing binding due to improper bellhousing alignment, bellhousing damaged, or loose. Clutch disc installed improperly. Clutch disc hub rubbing against flywheel bolts. Clutch disc binding on input shaft, damaged splines. Input shaft bent causing clutch disc runout. Pressure plate assembly and/or clutch disc bent or damaged. Clutch disc is too thick or has excessive Marcel (Too much cushion between the friction facings). Pressure plate has defective or damaged torque drive straps. Damaged, ...  more