Sounds to me since you seem to have the actual clutch sorted, that this is a master cylinder issue. You mention that you fitted a new lever recently! I would suspect the new lever is the culprit, not allowing relief of pressure!
Quite possible I guess! I shall try the old lever when I've a chance and let you know! Haven't had time with the 750 today as I've been playing with my 600 project!
Remove the 3 allens holding the slave cylinder and extract the actuating rod. These have a tendency to accumulate clutch powder and grime that eventually impedes or stops their full movement. I have been on a couple of rides when pals' bikes have started with clutch slip and ended up with no drive - same issue both times - the actuating rod not fully engaging/disengaging. Generally seems to happen after a period of inactivity, I suppose moisture and immobility married to the crusty build up results in a grimy collar round the actuating rod that just needs cleaning off.
