I have a Burman clutch on the Comet with 5 friction plates. all parts are in as new condition, there is no notching of basket or hub slots, all pressure and friction plates are new from VOC spares Co. It is correctly adjusted and plates separate squarely. It runs with engine oil in the primary case at correct level. However, when left for a period in the garage the plates stick together and are difficult to free. I put a tie around the clutch lever to keep the plates separated when left for long periods, then all is OK. Also when riding, although the clutch works OK, the plates still tend to stick. Anyone got any idea why? is it the friction material, could a different lubricant be beneficial?