This type of Allen head is what you need. The short side may still be too short to reach in with some sets, but just use the long end, and get some sort of tube to extend the short side you need to turn. I've even used a 1/4" deep-well socket for that.
 

You can also carefully wrap the inner shock tube in an old piece of rubber inner tube or leather and clamp it in a vise while you attempt to loosen the Allen head bolt.

At all my bikes the only way to get those bolts out was a pneumatic impact wrench.
Your local tyre dealer shoul have one.

Well, the problem has been found as to why the allen head bolt would not free up. The reason is that the top of the damper was broken off at the far end (top). This had fallen out into the oil bucket when I drained the old fork oil/water/tar mix, and I did not initially realize what was going on (the stuff that came out of the forks was amazing). I was aware of the need to keep things compressed a bit , but I think without anything that really grabbed the damper and keep it from turning, it just spun around.

Things became clearer once I removed the seal holder, and the tube came away from the lower leg. Then I could see the broken end, realized the issue, and was able to jam the fork spring down over the damaged damper to hold it, and loosen the lower bolt. I used my butterfly wrench, and made up a 6mm allen head tool by using a deep 6 point 1/4" drive socket with a piece of cut down allen wrench. The socket slipped into the lower leg fine. 

Neither one of my dumb strap wrenches would grab the shiny chrome of the seal holder. I used a heat gun to warm and expand the steel holder a bit, then wrapped a couple of turns of heavy duct tape around the holder and used a large pair of channell lock pliers on that. Once it started to move I set those down (HATED to use pliers there!!), and gripped as firmly as I could and was able to remove it (pretty fine threads right there on the leg).

Pics show the pieces cleaned up, I think the break at the damper top can be seen ok.



  

 

The right leg came apart without much trouble. It acted like most any other lower fork leg I have dealt with before (I have yet to tackle any upside down forks yet, so cannot speak to those). 

I did remove the lower snap ring at the very bottom of the left fork tube in a weak attempt to remove the damper remains for an 'inspection'. Could not budge the piston/guide the clip holds in place at all. Not quite sure how I would go at that. Kind of a moot point for me, though, as the replacement fork tubes I have for the bike both have the dampers already inside them. That may get set aside for a "later date" job.



  

This is the 6mm socket head tool I "made up". The small size of the socket allows it to fit into the bore of the lower leg ok, and the piece of 6mm allen wrench slips into the socket about 1/2", so it holds it well (I put a bit of contact cement inside to hold the piece in place). With this I can use my butterfly air wrench or a ratchet.

I do have a set of those ball-ended wrenches, and they are great, but I have seen the ends break off inside the head of the bolt if used with too much force (did that once in a difficult spot, a real pain to get out then). I now use a straight-on approach to loosen, then switch to the ball-end to finish up. Just my way I guess.

 

All kidding aside, Steve, I think I saw one of those on ebay two night ago. Just the damper rod, not the whole set of shocks or the whole single tube. Just what you want.

Bummer. Appears to be for the AT/CT line and not the DT. The DT is the same 68-70, partzilla says, though, if that helps...

Teardown continues. In the process I came up with a couple of observations that I was puzzled with. The first one is the small 'tang' on the frame crossmember that the rear fuel tank rubber band attaches to. It is not centralised! Note the offset to the left. There is no indication a second tang to the right was ever there (no obvious breakage/rust). Is this normal? Wouldn't the securing band tend to pull the back of the tank to the left a bit? I'm sure I could remove it and reattch it in the center, but if that was a "feature" of the '68 then I don't want to do that.Any comments? Is this the way they all are? 

 

The next point I noticed was the bend in the side stand. I am thinking this is probably something "normal" that happened with usage. Kind of hard to see in the photo but the bend is in the first 2-3" of the stand below the pivot. I anticipate straightening it before refinishing and attaching back on. 

I am kind of thinking they all do this??

 


 

Both wheels are now stripped of the tires and are totally stripped down. I put both up on my truing stand and they both ran very good. No appreciable wobble or hop, so I am thinking they should lace back up ok.

I acquired NOS spoke sets a few years back and will relace with those. New bearings/seals/brake shoes of course. The hubs and brake plates were splashed by something in proximity and whatever it was was never removed, and is proving difficult to remove with any solvent I have tried so far. But those bits were, I believe, a polished and clear-coated surface, so that will have to happen as well before assembly.

Turning to the rims, they are not awful, and if this were not what it is, I would probably clean them up real good and relace them. So I have to decide whether or not to have them re-chromed (estimate around $350 from one outfit), or get new reproductions for about half that (quality and appearance of these are not known to me at this point).

Pics are of the rear rim after a wire brush session on the inside and a hard rubdown with 0000 steel wool on one side, with the other side not done for comparison. I have asked for opinions on rims in another thread, but I want to decide soon.

Thoughts??

  

That is how they are