I know there are many posts on this strainer assy including Davids Spring fix under Restoration and Help. I have seen where some actually remove the adjustment knob to service the shaft Etc.. On the one that I have just repaired, the "pressed washer" was the problem having virtually disintegrated around the shaft. I removed the remnants of the washer with a set of cutters, Then I drilled two washers out that would slide snugly over the flange of the shaft. The first was a Nylon Cup washer to fit outside the strainer, The "Cup" facing the adjustment knob fits nicely to the curvature of the knob.

The second washer is around 1.5mm thick and replaces the pressed washer which origionally held the mechanism together. This is now held in place with an "E" clip which fits under the flange.

Although with this done, the strainer is now working as it was designed, I have also included a spring as per Davids mod. The spring gives a nice positive action to the lever operation..and the "E" clip stops the shaft from exiting the housing.

I hope this may help someone,,

Cheers