From post above, to remove the original flathead screws that may have a damaged slot: "I used a small .25inch pin punch, about 6 inches long, it barely fit between the solenoid body and the exhaust pipe, and I nicked a ridge into the passenger side of the roundhead slotted screw head, then a tapped it with a tack hammer to rotate free. It was mild steel, so a fresh hardened punch bit into it pretty easily."

To reinstall and adjust...
1. Buy a set of ball end hex wrench sockets. Makes everything much easier. The exhaust is in the way. There's no way to futz with the adjustment in the small space remaining.
2. Replace flat head and hex head screws with 10-32x.5" allen-head (socket-head) screws (4-5 required.)
3. FYI You have to remove the return-stop cap to get the nut off the plunger stem.
4. with the solenoid removed, note the depth where the plunger stops. (Note the additional 1-2mm "springy" depth after that, which is to disengage the 30amp high actuating current and use only 3amp holding current)

5. Loosely-mount the solenoid and plunger (without the plunger nut) and set the plunger to stop depth. With the 3/16 drill/pin through the arm, count the threads still showing. Remove the solenoid, so you can grab the plunger with a soft plier, and turn the nylock nut onto the plunger stem until the counted thread depth is nearly covered. A turn loose is better than tight.
6. Remount the solenoid body and check the stop depth again. There should be daylight (barely) between the pinned lever and the nut.
7. Replace the stop cap, leaving a couple full turns of space above the end of the plunger.
8. Safety wire the stop nut to the drain nut. Very fine wire, tricky to find the hole. The flat head of the screw should be about flush-even with the top of the castellated nut. Remember you are screwing into an aluminum thread: do not overtighten.

I did it twice, once super-precise, which turned out to be too tight, and it engaged automatically in 1st, which annoyed and scared me.
--
MPergiel, Walker, MI