I'll explain the same issue in different words - Deejay, please put me right if necessary. The half of the clutch that is attached to the crankshaft is only retained by friction, using a captive cotter pin. Sometimes this slips a bit, resulting in the clutch-half moving up against the engine. The clutch then lacks clamping force even if adjusted with the adjusting nut. To fix this, undo the adjusting nut as far as possible. This releases the clutch spring. Then loosen the captive cotter pin, and lever the crankshaft-attached half of the clutch along the crankshaft until it is 1 cm from the side of the engine. Tighten the captive cotter pin, then use the clutch adjusting nut to properly adjust the clutch so it works correctly.
