I got your email, I have a replacement fork in the works for you right now (paint is drying!), the one I'm doing is the "r2" (860296-r2) revision with the thicker beam cross-section.
As for the flywheel dust cover, I've only seen one version for the Scout 80, there was only one transmissions setup offered for Scout 80 also. It's a fairly light gauge sheetmetal cover.
All the Scout 800/four speed (pancake bellhousing for the t-18) dust covers used with the 152 and 196 engines are plastic. I have two of those. However, I know I've not seen all of everything that was ever available, it's possible that some steel dust covers were used on some models. The 152 and later the 196 engines with both three speed and four speed trannys were also installed in some pickups, those May use another variation dust cover, I don't know right now if they used the pancake bellhousing common to Scout 80/800 or not. I'd have to deeply research that!
If your dust cover is indeed heavier gauge, and the slot is not proper for the travel of the slave/pushrod, then it's possible that the fork could be bent by the tremendous pressure the master/slave can generate (about 1500psi) if the fork bottoms out before the slave is extended it's normal working distance.
What you describe regarding the slave not retracting, tells me the piston is cocked in it's bore, that indicates a hyper-extension! There is no one-way check valve in either the master or the slave, that system does not use a residual pressure valve as found on brake hydraulics. The bore size on the oem cylinders must match, they are both 5/8" bore oem. They are also available in 3/4" bore size. Total available "working" travel distance of that slave is 1", however when everything is correct and all parts are new/rebuilt, the actual travel distance from slack pedal to full clutch release is about 3/4" nominal.
If needed, certainly relieve the slot in the dust cover so that no contact is made between any component and the slot. In fact, when you re-assemble, leave the cover off and test drive for several miles, that hurts nothing! Then you can look up inside and observe all the relationships between the clutch release components.
We're sorry you are having such a problem! But this is a very strange deal and we need to add to everyone's knowledge base here! Of course, there is no charge on your part for the replacement part I'm sending you and it will have a new pivot bolt setup (and bushing) also, so be sure to enclose the old one with the bent arm when ya return it, that will also help me figgr out what's going on here!
I have n=5 forks here for cores now, two are the r21 version, the other three are the r1 version. The "bend" in the lever on all is exactly the same. One of 'em shows signs of a po grinding on it where it comes close to the slot though, I bet someone did a swaperoo and found that one made contact also and tried to modify the arm. I've welded it up and reground so it is now useable.
The r1 version does not appear in the last gen Scout 80/800 parts list, nor does it appear in the cross-reference or the price list which is used for crossing part numbers also.
By the way, I was wrong about the four banger s800 not using the hydraulic clutch actuator, the right-hand drive version did use a hydraulic clutch, as did "some" left-hand drive, there was a production change according to the parts list.