My forks had way too much stiction so i researched the issue. I found low friction seals made by SKF that have the right ID and OD dimensions. The width was different, (9mm?) so I made spacers to suit from aluminum.
They are listed as fitting lots of Jap bikes with 41mm Showa forks. OD: 54mm. One kit does one fork leg. They are 2 piece green color, upper and lower. I only used the lower oil seal. At the time of writing, they are $39USD per side. Sales pitch says 20% less friction plus longer lasting. It's a difference I can feel.
I ended up having one spacer below of about 1.6mm thickness plus one above of about 4.5mm thickness. The upper one, I machined a small step in the ID to clear the seal lip.
Pic: parting off spacer
On the lift getting the treatment. The fork tubes were slightly splayed apart at the bottom, so I had to doctor the upper fit to top triple tree. Mine is repop parts so much of it isn't well machined. In pic below, I made a distance piece to mimic the front wheel, basically a piece of tube with small flanges either end. In this way I could test by hand the friction, stiction and trial various configurations.
Here with the bikini tool bag
Under the dust covers, I made sponge lube wicks. Currently I spray teflon dry glide on these but may trial other lubes as I go along.
16Mar23
I got a nice improvement with on-road-feel. The front end "gives and soaks up bumps" more on hard edge bumps which is what I was looking for. It will never be a modern suspension, but I enjoy some improvement.
Update with some good progress. The solutions were in a number of steps which I'll itemize in detail. Till now, I was still getting 30mm - 35mm of stiction.
I made a solid distance piece tool, to measure the legs for being parallel. This was like using an inside micrometer but a fixed length. In this way I was able to understand, the legs were slightly splayed.
I used an old drill press table-plate to check fork tubes were parallel to each other when viewed from the side. Historically I used to simply eyeball this, but the little machine finished table took it to another level.
The top fork tube plugs were not concentric to the tube itself. At least some of the problem was in the tube thread, it was off center. To fix this, I screwed the plug in tight, then put the tube in the lathe, holding the top end in a steady. At this stage it was obvious how far out of true the assembly was, so I turned some material away. Clearly it would be slightly loose in the top tree but that was better than being somewhat bow legged. These are repop, so I simply did what I had to do.
I read about low friction fork seals made by SKF, green color. They are $40USD a side. Not cheap but they made a very noticeable difference when comparing by hand one against another with existing seal. These SKF seals were not listed as fitting a FXWG or any Harley but I was able to verify inner and outer dimensions. I did not care what the thickness was because I'd make spacers to suit. Their dust seals weren't used.
I pulled the gold valves, removed the recommended compression damping springs and replaced them with the lightest one in the kit, setting them just 2 turns of preload.
I polished the fork spring outers with fine wet and dry.
I researched oils, looking for any small margin of reduced friction. I settled on synthetic fork oil by Motul Factory Line. I chose 10w, their heaviest in synthethic.
Fork tube treatment. PTFE Teflon spray was tipped as an aid to reducing stiction. Apparently racebike guys use it. Of the types I had on hand Dry Glide seemed to have superior film residue so I've been applying that before every ride.
PTFE grease is available from cycle shops so considering trialing some, perhaps on sponge rubber under the dust caps.
Update 17mar23 I cut some thin strips of sponge, soaked them in oil and wrapped them around each tube under the dust cover. To be tested once it stops raining...
Result to date. Front end has transformed. I can feel the difference and I can see the fork sliders becoming more responsive. It's gone from being too solid on hard edge bumps to soaking up bumps more and more.. At the moment I'm continuing to work on more improvement so will post result.
24mar23 Fork oil was swapped to 15w, full synthetic by Putoline.
Grease with PTFE was applied to fork tubes which made a great improvement to stiction.
