Armen
Serious Thumper
Offline
Half-Witted Wrench-Jockey from Jersey
Posts: 1452
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So, once I read Gary's excellent fork fondling article, I decided I had to do mine. Over the course of way-too-long, I bought the Race Tech Emulators, Race Tech springs, a good used front end (so the bike wouldn't be beached while twiddling the forks), all the seals, clips, allen bolts, upper and lower bushings, crush washers and whatever else I could think of. There was an article titled 'Deslopping the Sliders' in Motorcyclist magazine in the 80's written by Joe Minton based on some work done by Pierre DesRoches (very good Kawi tuner). Around that time, the practice of using upper and lower Teflon coated bushings in forks was becoming commonplace. The good news is that the fork tube would be sliding on a slippery, replaceable bushing. The bad news was that the fit was often less than airtight when new, and got looser as the miles accumulated. The gag was to remove the lower bushing from the fork tube, place a piece of shim stock underneath it, reinstall the bushing, and check the fit in the lower leg. The idea was to go up in thickness on the shim stock until the fork tube showed resistance when slid into the lower leg, then go down one thickness on the shim stock. I've done this on more than a few bikes. Sometimes no shim is needed (usually with new parts), and sometimes as much as .004" shim stock was needed. The upper is a bit trickier. The upper bushing is pressed into the top of the lower leg, so a shim can't be fitted. The routine is to lay the bushing on the fork tube and dimple the outer surface with a center punch. The bushing and the fork tube are then reinstalled and checked of slop or binding. If there is slop, more center punching. If there is binding, then the dimples on the bushing are reduced by wiping them with a sharp flat file. So, off I went. With new lower bushings, the fit of the fork tubes in the lower legs was perfect. No slop and no drag. The uppers were another story. I could move the fork tube in the top of the lower leg. The bushings were removed and dimpled. The article also said to take a wipe off the edges of the bushing where it came together to allow the bushing to become a smaller circle. On the first go, the fork tubes bound up. I removed the top bushings and filed a little off the center punch dimples. The second try was perfect. No slop and no binding. I modified the Emulators as per Gary's article. Different springs, more holes, different preload. One fork tube showed slight wear marks. On bikes with a single disc and minimalist fork bracing, I've often stood on the pegs and looked over the bars at the front end while grabbing the brakes. You can actually see the front end rotate as you grab the front brake. i swapped the legs so that the less worn one would be on the disc side from now on. I'm hoping that with the more butch top clamp and the TKat fork brace, the front end won't twist as much or as easily. In reassembling, I realized I had lost one of the washers that go under the fork seal. A 1/2" fender washer has a similar OD, so a bit of lathe work and I had a god substitute. The whole mess went back together pretty easily. A bit of Race Tech seal grease on the ID of the fork seal. 10W fork oil (on another of my bikes, the 15W that Race Tech suggested was too thick) filled to 150mm from the top. As per Gary's article, I bought a set of pre-load adjustable caps, a nice touch. I'm figuring that it'll need some tweaking, but I'm hoping it's pretty close. Gary is a bit heavier than me, so some of the specs that work for him might not work for me. Children won't die. I'll sort it out. It has to be better than the stock crapola. Thanks to Gary for all his experimentation and thorough write-up.
In the pic are the Race Tech springs and Emulator. A fork seal/bushing instilling tool I made, the upper bushing showing the center punch dimples, seal grease, and some other parts.
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