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Old 08-04-2013, 06:49 PM   #1
JonnyCash OP
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Are /5 fork tubes and dampers the same as /7?

Or at least can I use them in /7 sliders?
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Old 08-05-2013, 07:51 AM   #2
jsullivan
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I'm using /7 tubes in /5 sliders with no problem.
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Old 08-05-2013, 09:34 AM   #3
Big Bamboo
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They are all the same up to 1980, but lots of changes in the years following.
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Old 08-05-2013, 05:32 PM   #4
Voltaire
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I've got post 81 sliders and internals in a set of ATE disc lowers, straight drop in, need to drill hole at bottom from 6mm to 8mm from memory.
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Old 08-05-2013, 05:47 PM   #5
bmwrench
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The tubes are the same from 1969-1980. The dampers changed quite a bit as the years and models went by. If your /7 dampers are useable, you should swap them into the /5 tubes, as well as the damper nozzles at the bottom of the tubes.
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Old 08-05-2013, 07:07 PM   #6
JonnyCash OP
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Thanks for your replies, here's what's going on. I just rebuilt the forks on my /5, which has a bunch of stuff from a, r100S, including the front end. The fork action has been terrible for awhile, but rebuilding it for a long time has fallen behind other more pressing things. When I got into it, I found that the rubber bump stops, upper and lower, were totally disintegrated, not a big surprise. I also, found that the chrome on the fork tubes was badly worn. They were about the same on each side, worn on the front at the very bottom, and on the back about a foot up, which makes sense to me. I didn't see any corresponding wear inside the fork legs, but it's kind of hard to get a great look in there.I replaced everything that came in the rebuild kit, except the wiper rings as seems to be the consensus. I cleaned everything out, and I rotated the fork tubes 180degrees, so that the worn spots should go opposite where they had been before. I figured I'd see how it went, and keep my eyes open for some good used parts to put in later.

I put everything back together carefully, and while I didn't go the full course with the plate glass etc, I did pay attention to keeping everything aligned as I put it all back. The fender brace took a little shimming, but when I was done, the axle would glide in and out better than it ever has before for me on this bike, better than I would have imagined possible actually. Before I secured the damper rods to the bottom caps of the fork legs, the legs with the fender and axle secured would slide up and down just a slick as you please. I felt like it was a victory, but I didn't yet have fork oil to put in. I went to my local (shitty!) cycle shop to get fork oil and the lightest they had was 10 wt so I bought it, even though I had wanted 7.5. I also put in the preload spacers. I took it out for a ride, thinking it would be bliss, but oh my god it is so stiff and sticky it's just awful! I drained out the oil, replaced it with ATF, having heard it worked okay in a pinch, and removed the preload. It might be a little better, but it still sucks.

Do you think it's the oil? Worn fork legs? Something else? I appreciate any suggestions. I have another /5, which I will one day rebuild, but right now I'm kind of in recovery from my recent Guzzi project. Anyway, I could pull it apart to see if the fork tubes are better on it and use them, but somehow I dont feel like that is the root of my problem here.
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Old 08-05-2013, 08:10 PM   #7
east high
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Armchairing this advice as I haven't yet done my forks, but stiff and sticking sounds like stiction and a combo of heavy oil and preload shims. You might start over with 5 or 7.5 fork oil and no preload shims. Once that's sorted you can move on to the fussier job of removing the stiction.
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Old 08-05-2013, 09:22 PM   #8
Big Bamboo
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My advice would be to get that piece of glass. 7" x 9" piece of thick glass works well. Quickest and easiest way to be sure everything's in the same plane. Once you know that, try this. Tighten the axle nut, but leave the pinch bolt on the other side loose. Now push the loose slider in and out on your clean greased axle and note the amount of movement. Using your calibrated eye ball, position the slider in the middle of that movement on the axle. Tighten pinch bolt. Small adjustments make big differences. Before adding the new oil, try grabbing a handful of front brake, to keep the bike from moving forward, and push down hard on the front end, to feel any sticking.
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Old 08-07-2013, 08:07 AM   #9
Pokie
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After years of messing with forks, this is what I do to keep forks working properly through the assembly process. Rather than trying to fix a problem later, I try to correct problems before they become a problem. This works for me.

When I'm putting together a set of forks, I never put the springs or oil in until the last moment. I'll assemble the forks into the yokes with out the brace or axle in place. Put the top nuts on without the springs (don't tiighten). Slide the axle in, leave the wheel off. Put the nut on the axle but don't try to tighten it as there's nothing to tighten to. Grab the axle in the middle and slide the forks up and down, how do they feel? If there is any stiffness, address it now. Try rotating the fork legs (one at a time) to see if there is any better movement in a different spot.

Now that the forks have been slid up and down a few times, tighten the axle pinch bolt. Slide the forks up and down, any change?

Tighten the top nuts, slide the forks up and down, any change?

Tighten the yoke pinch nuts, slide the forks up and down, any change?

Set the fork brace on and thread on the nuts but DON'T tighten them. Slide the forks up and down, any change?

Tighten one side of the fork brace, slide the forks up and down, any change?

Look at the other side of the fork brace, any space between the fork brace and the lower leg? If there is any space or if the brace fits crooked at all, the moment the brace is tightened, the forks WILL bind. The fork brace must be "tuned" to fit both lower legs perfectly. No shims, no nothing,... it must be tuned to fit perfectly.

Each time anything on the forks is assembled or tightened, the forks must be tested. If there is any tightening or stiffness, you have to go back that step and figure out what went wrong and fix it. The forks MUST move freely BEFORE oil or the springs are added.
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Old 08-07-2013, 10:15 AM   #10
Big Bamboo
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Also, when torquing the top nuts, I use a counter lever to avoid twisting the assembly. Two bolts with locknuts in the riser mounting holes and a very large screwdriver is sufficient.
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Old 08-07-2013, 03:00 PM   #11
JonnyCash OP
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Thanks for taking the time to explain a lot of the process. I am somewhat familiar with a lot of it, but really I've never had trouble with a sticky fork before, and I've never really made much of a fuss over when assembling things in the past. The way I see it though, is that if the axle goes in nicely, and it really does in this case, doesn't that say that things are aligned well? I need to get my hands on some lighter oil and try it, before I go through all sorts of gyrations trying to fix what isn't broken. Does anyone here use ATF happily, or 10 wt? Thanks again, all.
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Old 08-07-2013, 11:25 PM   #12
Wirespokes
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I used to use ATF thinking it was around 7 wt. Was told by a knowledgeable oil guy it's more like 15. I think your idea of going to lighter wt oil is the best first step.
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