Does the longer fork leg also compress and expand normally ?
If you're going to disassemble the forks, first take off the drain bolts on the back sides of the sliders and drain out the old suspension oil. Note if there are chunks of black plastic or goo in it. You should be able to get at least 150-190cc of oil out each leg. Put the drain bolts back carefully - DO NOT TIGHTEN THEM to the 10 FT-LBS you'll see in some manuals as you can strip the aluminum threads - just snug them up reasonably such that the don't leak oil after you refill everything.
Don't give up hope yet - the allen bolts on the bottoms of these forks can do what you describe (spin around without seeming to tighten)if the damping rod assembly inside the fork lowers is also turning. IF you haven't been getting oil leakeage out that bottom bolt hole, then the bolt is indeed tight (or you have somehow already lost all the oil in that fork leg). To loosen/tighten that allen bolt to take the sliders off for disassembly, you'll have to take the top cap off the fork leg. Inside there is a metal "plug" which is retained by a circular spring retainer that fits in a groove milled into the interior of the fork tube. You have to push down on the plug (against the pressure of the spring) to get it far enough down below the retainer so that you can pry the retainer out of its groove with needle nose pliers and/or small screwdriver. DO NOT LOSE IT!
Also, be careful letting the pressure back off the spring unless you want to catch the metal plug in your eye..
Usually the spring pressure is enough to pop the plug out the top but sometimes it may get a little tipped to the side on its way out and hang up inside the tube - just push down on it again and let it up until it comes free. If the spring inside is broken, it might not pop up - and that could be one possibility as to why one leg is longer than the other.
Anyhow, pull the spring up out the top of the tube. It it is an aftermarket spring, you might find a plastic PVC spacer in the tube as well. NOW that you've finally got all that out of the way, you will need a socket wrench with a looong extension on it to reach down into the tube and grab onto the nut at the top of the damper assembly. I *think* that the nut size is 11mm, but my memory isn't good at the moment. Holding the socket wrench at the top from turning, you can now go back to the Allen bolt at the bottom (remember that is what got us started down this path?) and you should be able to loosen it while holding the other end of the damper tight with the socket wrench. This all seems like it requires a 3rd hand, or a second person to help, and sometimes it does. Once you've got the bottom bolt loose I will usually take the fork tubes off the bike so I can lay them on a bench, slip off the dust caps from the top of the sliders, and slide the tubes and internal damper assembly out from the fork sliders/lowers.
There is supposed to be a bit of spring pre-load in these forks - dpending upon the length of the springs installed one needs an appropriate spacer or you may here alot of clunking/noise happening when the fork compresses/extends. The Progressive spring kit I installed in my 82 came with 1" spacers to get thr right amt of preload.
Keep us posted and we'll try to help you out.
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