Zorki 5 & 6 lever wind CLA
The lever rewind on these Zorki models have been the subject of much criticism for being rough and crunchy. Perhaps it will never be as buttery smooth as a Leica M but it can definitely be CLA'd not to sound like an unsynchronized manual gearbox.
First step is to take off the top RF cover follow this link for a pictorial diagram of the procedure. Note that on the early "rare" Zorki 5 with a square RF window and engraved "red logo" the round nut is turned counter clockwise.
Once the top is removed this is what you will find......
Zorki 5a
Now is a good time to flush and clean all the gears using lighter fluid with generous burst of compressed air and a brush to remove all the accumulated grime and dirt.
Loosen the 3 screws [1, 2 & 3] securing the bridge [4]. On the Zorki 6 there are 4 screws [and possibly later Zorki 5s]. You will notice that the bridge is now loose and moves laterally. To keep things simple loosening the 3 or 4 screws will be enough to clean up the gear set. However for thorough cleaning the bridge can be removed to gain full acces to the gears underneath, But make sure you document every step of your procedure with a digital camera or else you might have a hard time reassembling the shutter release linkage underneath. Carry on with flushing as much dirt as possible from the gear set under the bridge.
After cleaning this area thoroughly use some NYOIL or equivalent to lubricate all accessible and visible gear pivots and then pack the gears with Castrol GTX grease. It might be a good idea to retighten the 3 screws or reinstall the bridge assembly and then temporarily mount the lever wind to spread the grease evenly on all the gears by winding and firing the shutter.
Since you are already there, it might be a good idea to clean the shutter mechanism and lubricate the coupling pin lever bearing.
Zorki 5a
Smooth winding is achieved by finding the most "ideal" coupling between gear 2 [drives the film sprocket underneath] and gear 3 which is part of the bridge [1]. With the lever wind temporarily mounted, wind and fire the shutter to adjust the bridge orientation for "best feel" Then tighten the 3 or 4 screws on the bridge and reassemble.
Note [4]: Maizenberg states that damage to the rangefinder is possible if the Zorki 5 is fired without a lens mounted. If you observe the picture above carefully [lens attached] when the lens is removed the rangefinder arm [4] will move inwards and if the spring holding it buckles completely the RF arm will be in the way of the rotating coupling lever when the shutter is released.