Sticky fork tubes

[Dogma]

Hello geniuses (genii?),

I haven't updated my project thread, but I've been riding my 1000G for about a few weeks now. Like Griffin said, the 850 is great, this is just more of a good thing. Lovin' it. Lovin' the G seat too. But all is not well. At highway speeds, the bike is very stable until I come up behind anything the size of a minivan or more. It gets a pretty spooky wobble that's bad enough to get my knees swaying. Obviously, I avoid that now, but I shouldn't have to. If I have to bee in that spot, some light swerving in the lane keeps it steady.

In my quest to diagnose this, I noticed last night that my forks are sticky. They need some encouragement to either compress or rebound. OK, so I took steps this morning to make sure the legs are parallel, with no change. OK, so I took the wheel off. No change. Each fork leg requires a lot more effort than I expect to move it, even with the springs out (was going to install the Progressives while I was in there). Even twisting the fork lower exhibits not-at-all subtle stiction. Just for a sanity check, I walked over and bounced the 850 a few times. No detectable stiction, just like I thought it should be.

I rebuilt these forks last fall when I started the rebuild, and didn't notice this. I wasn't looking for it either. But the front end has never been smooth through the probably 1500 miles I've put on it. I don't remember what brand seals I used, but I most likely ordered them from Z1. Fork oil is 15wt.

The short version: What can cause stiction in individual fork legs?

Thanks in advance.

[posplayr]

Hello geniuses (genii?),

I haven't updated my project thread, but I've been riding my 1000G for about a few weeks now. Like Griffin said, the 850 is great, this is just more of a good thing. Lovin' it. Lovin' the G seat too. But all is not well. At highway speeds, the bike is very stable until I come up behind anything the size of a minivan or more. It gets a pretty spooky wobble that's bad enough to get my knees swaying. Obviously, I avoid that now, but I shouldn't have to. If I have to bee in that spot, some light swerving in the lane keeps it steady.

In my quest to diagnose this, I noticed last night that my forks are sticky. They need some encouragement to either compress or rebound. OK, so I took steps this morning to make sure the legs are parallel, with no change. OK, so I took the wheel off. No change. Each fork leg requires a lot more effort than I expect to move it, even with the springs out (was going to install the Progressives while I was in there). Even twisting the fork lower exhibits not-at-all subtle stiction. Just for a sanity check, I walked over and bounced the 850 a few times. No detectable stiction, just like I thought it should be.

I rebuilt these forks last fall when I started the rebuild, and didn't notice this. I wasn't looking for it either. But the front end has never been smooth through the probably 1500 miles I've put on it. I don't remember what brand seals I used, but I most likely ordered them from Z1. Fork oil is 15wt.

The short version: What can cause stiction in individual fork legs?

Thanks in advance.

Stiction is a form of friction. With the springs out and the fork drained they should slide easily. The friction points are primarily the teflon coated sliders at top and bottom of the fork. The seal probably provides some but oiled rubber sliding on a chromed surface would likely not produce as much as the surface area of the sliders.

I would suspect you might have something assembled wrong, they should be relatively smooth.

[Dogma]

...
I would suspect you might have something assembled wrong, they should be relatively smooth.

Yeah, I thought they should be smooth too. Not much to get wrong in individual fork legs. I'll be disassembling them later this weekend looking for more clues inside. I'll report back for posterity.

[jetta90]

While you're in there checking things out would be good to ensure the fork tubes are perfectly straight.
If the bike's history in unknown it could have had a bit of an incident in the past. Possibly a minor impact ever so slightly bending the fork stanchion(s).
Just a thought.........

[Macmatic]

....but oiled rubber sliding on a chromed surface would likely not produce as much as the surface area of the sliders.

They ARE oiled, right? I mean it would be hard to do but when I was reading your first post I wondered to myself if the seals were dry. Maybe hit the tubes with a little wd40 or something to lube the outer lip of the seal and try it to see if it makes a difference.

/\/\ac

[posplayr]

Yeah, I thought they should be smooth too. Not much to get wrong in individual fork legs. I'll be disassembling them later this weekend looking for more clues inside. I'll report back for posterity.

I have been pulling mine as well. APPARENTLY the race tech emulators were not properly installed

I'm having to pull the damper rods and drill above the lock piece (resting now)

They are back on now comes the the part about making sure all are aligned after the wheel and fork brace are on.

[Dogma]

Well, here's what I found in there. I don't remember seeing rub marks last fall when I had these apart. My project thread only shows pictures of gouges in the outer tubes. I can't feel this with a finger or wipe it off. I haven't tried buffing yet. There are matching rub marks on the Teflon-coated ring, and a spot on the bottom of the stanchion is very polished-looking. I may have done that polishing last fall to clean up gouges on the bottom of the stanchion.

Both legs show similar symptoms. I'm guessing I didn't do nearly as good a job as I thought getting this front end put back together and aligned. Or is this sort of wear typical with the hoop-style brace? The width of the hoop would need to be correct to a tolerance smaller than the minimum clearance in the two fork legs. If I designed a fork brace, I wouldn't try that.

What I don't get is that the stanchions are sticky within the tubes with absolutely no external load. In fact, they're only sticky when the seals are engaged with the tube. In other words, it's the seals doing the sticking. I think what I'll do is put it back together without the hoop brace and see how that behaves.

Are some seal brands more slippery that others?

[gmansyz]

How did you get it apart without removing the retaining clip and seal? And washer in-between?
G

[TheCafeKid]

How did you assemble the front end when you instAlled the brace? With any fork brace you should have had the weight off the front, wheel off, and all bolts for the trees loose. Install the brace and tighten from the top down checking for bind along the way.

[Dogma]

How did you get it apart without removing the retaining clip and seal? And washer in-between?
G

??? On these forks, there is a screw at the bottom of the fork leg that threads into the damper rod. This is the only thing holding the stanchion in the lower. The seals don't interfere at all with removal. Except for some stiction.

[Dogma]

How did you assemble the front end when you instAlled the brace? With any fork brace you should have had the weight off the front, wheel off, and all bolts for the trees loose. Install the brace and tighten from the top down checking for bind along the way.

I did not follow that procedure.

Things were complicated by the fact that the wheel can't pass between the forks after the brace and fender are bolted in. The tire won't pass the screw heads. IIRC, I mounted the wheel and tightened the axle with the fender and brace loose. Then I snugged the lower clamps and bounced the front end a few times to line things up. Tightened the top clamps and the top triple to the stem, bounced it again to see if anything was binding. Then tightened the brace and checked again for binding. Clearly, all that didn't work. The rubbing presumably caused by the brace was completely masked by the stiction in the seals, and bouncing the bike didn't give me any feel for that either.

Does your procedure assume that the triple-clamps are already aligned? Without the axle tying the folks together, how do you make sure the tubes are aligned before you tighten them?

[RageZro]

I would have let the axle float in your procedure.

I have done mine a little different than what I'm reading here. After a fresh rebuild I have the wheel on the axle still loose in the forks, the fender/brace on but loose and lower tree clamp slightly loose with the top tight. No oil in the tubes yet and the springs in but no caps on.

With the bike perpendicular to the floor, wheel straight forward, I collapse the forks all the way down until the inners bottom out. If you think about it, the bearing surfaces in the forks are at their maximum distance apart when the forks are fully depressed into themselves. That means the the fork is expressing its least amount of flex from end to end so it is as true straight as the fork can get.

Tighten the lower clamp and then the axle to the specific torque (not a good time to use "purtineer"). It really requires a helper to keep the bike upright unless you can put in on the centerstand and raise the rear without causing it to collapse the stand. It must not lean or it's all for nothing.

The fork brace and/or fender are the last to be tightened. You have to look to be sure they are a snug fit between the forks before tightening, if you have to draw them up to take out an air gap between the brace and the fork then there is a problem (bent brace, bent forks, wrong brace/fork, missing spacers). Best to stop at this point and see what is going on.

If everything lined up well and is now tight to spec, then raise the weight off the forks so the forks are now fully extended with the wheel suspended in the air and fill the forks. I prefer to measure the height of the oil in each tube versus just depending on the volumes being the same, should provide a better match side to side. Cap them and test ride it.

If you have binding at any point when compressing them after assembly, then something is most likely bent if you put the dampers in correctly and the correct weight oil. If you have access to a tooling plate table before you reassemble you can roll your inners on it and watch for gaps to be visible between the tube and the table as it rolls. A few machine/fab/weld shops still have these ground plate tables.

The photo is not a good sign and I'm guessing either you need to try the above or you already have something bent unless the brace is introducing binding when you tighten it up. Spacers might not be an option as they generally introduce flex depending on how hard you push the suspension.

Good luck and get that thing back together before next weekend!

[Nessism]

To add to the above procedure, you want to pump the forks at each step to align the parts before tightening the bolts. I usually start with the lower triple clamp bolts tightening first, then pump the forks and go to the next series of bolts, etc.

[Dogma]

Jim, you pretty much describe what I was thinking about doing: caps off so the forks can be compressed completely. I was able to do the 850 without trouble having the springs active, but I'm eliminating every possible problem this time. My only deviation from you plan is what Ed suggests. The top clamps just floats on top of the stem, so tightening it first will just fight the rest of the system.

What you said about the center stand is real easy on the GS shafties that still have the center stand. There's a place you can slide a pin (such as a semi-beefy screwdriver, or a 3/16" or so inch Allen wrench) that prevents the stand from collapsing while you have a wheel off. With the weight of the front wheel off the bike, it's almost perfectly balanced on the stand.

Thanks for the input. I hope it works. I wasted a chunk of this evening running down a fresh stash of fork oil. I should be able to get it back together tomorrow evening.

[Dogma]

Just a follow up here...

I put it all back together in the spare time I had over the last couple nights in this fashion:

Fork reassembly procedure:
1 Top triple clamp loose on the stem and stanchions.
2 Wheel installed, axle and clamp nuts loose.
3 Lower triple clamp just snug enough to hold the stanchions in.
4 Caps off so the springs won't hold the bike up.
5 Floor jack under the bike holding it so that the forks are about 10mm from fully compressed.
6 Tighten the axle nut, leaving the pinch bolts loose. This allows the fork leg spacing to adjust itself.
7 Raise the front end to check for binding, lower back down.
8 Tighten the lower triple clamp.
9 Raise the front end to check for binding, lower back down.
10 Tighten the top triple clamp, stem nut, stem pinch bolt.
11 Raise the front end to check for binding, lower back down.
12 Tighten the axle pinch bolts.
13 Raise the front end to check for binding, lower back down.
14 Install fender and brace.
15 Raise the front end to check for binding, lower back down.
16 Raise the front end to full extension and install the spring caps.
17 Brake calipers, handlebars, etc.

I did everything but 14b and 15. My thinking was to eliminate any possible problems, as I plan to ride it this weekend, and I don't have any more time to dink with this right now. At any rate, stiction is noticeably reduced, with just drag from the seals.

So I finally had time to take it out this evening to see if the truck-induced wobble is cured. I got out on I75 and tailed every truck I could find, which wasn't many. They all seemed to be going the other way. Where's an obstruction when you need it? Anyhow, I got behind one that was throwing my upper body around pretty well, but the bike was steady. Success! She's also noticeably less harsh on the bumps.

I think where I went wrong before was leaving the axle pinch bolts tight. This time, I actually went a couple round with them because the forks would drag a little more when I tightened them. With the axle pinch nuts loose, I could move the folk leg as much as 0.5mm back and forth along the axle. I eventually found a spot to tighten things up where no more drag was added.

When I have time, I may try putting the brace back on to see how that behaves. Thinking about it, I don't like this hoop brace design. The spacing is fixed, so it can't be adjusted to any variation the forks may have.

I also installed Progressive springs and added a few psi to the front tire. She rides great. I'd say the front end is squared away. Next problem after the break.