It's been discussed in the past but thought the subject worth revisiting.
The lever on my Bezzera E61 has become quite notchy/sticky to operate over the past few weeks, it had even started to squeak a little, so I pulled it apart and lubricated it, a dab of grease really makes a remarkable difference.

Link to parts diagram
Coffee Parts | ECM Spare Parts - Group Head e61 Lever Operated
The solution is to lubricate the assembly with Inox food grade grease available from Jaycar, the only tools required are a large adjustable spanner, large screw driver, tweezers and cotton bud.
Remove the handle, unscrew and remove the mushroom assembly, lift out the spring and valve, using the spanner unscrew the body of the shaft assy 460078 remove the assy including the shaft and cam in one piece, withdraw the shaft 461102 and dry everything off, then lubricate the shaft and cam with Inox.
Reverse the procedure to reassemble.
In the past I've been told lubrication is not necessary (coffee oils will do the job) not so, I find that if you back flush regularly using one of the chemicals designed for the purpose the process strips all of the oil and grease from the assembly leaving the parts as dry as a bone, and the lever feels and sounds horrible.
It's an easy job, start to finish no more than 10 minutes.