Yesterday I had the unnerving experience of my clutch lever coming right back to the bar with no resistance. This happend a couple of times during the day. Immediately afterwards the thing behaved as normal. I have a stock unit; master and slave.
So I duly dismantled the master (all ok) and replaced/bled the fluid. Today (touch wood) it's ok.
Anyone had this happen before? Any ideas what could cause such an intermittent problem?
Check the fluid level and try a good bleeding before anything else. A small air bubble can grow into a bigger air bubble when warm. Next I would suspect the slave, particularly if it is the original and the fluid level is low. Remove the cylinder and look for brake fluid coming out of the weep hole.