Are my ST1100 fork springs shot?

paulcb

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Here's what I'm experiencing with my 2001 ST1100 with 53K on it...

During front braking to full stop (i.e. at a redlight), the front forks compress (as expected), but after stopping they do not fully return to the neutral position, they stay fairly compressed. I can either pull them up while stopped or they return when accelerating from the stop. The bike seems to handle just fine though, at least for the riding I do.

Here's the background...

Purchased the bike in summer 2013 with 36k on it. I noticed this "phenomena" shortly after purchase. At 46K, I had a leaky fork seal so I rebuilt the forks, keeping the stock springs. The rebuild went well using a borrowed fork seal R&R kit (see this thread for details). At the time, it seemed the rebuild resolved this "no return" phenomena. Now with 53k on it, it seems to have returned.

So, my questions are... is this "no return" normal? I don't remember this on any other street bike I've had but may not have noticed it in my younger years. If not normal, is it a spring issue or something else?

TIA for your help.

Regards,
Paul
 

ST1100Y

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Definitely not normal...
Could be that a fork tube is bend/oval, could be that the fork tubes are "twisted" in the triple-clamps, could be one/some of the glider bushings are damaged, etc...

Did you recently hit a pothole or ran over a curb?
 
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Could be that a fork tube is bend/oval, could be that the fork tubes are "twisted" in the triple-clamps, could be one/some of the glider bushings are damaged, etc...
agreed. The triple clamp twisting possibility can be easily checked by looking down from above the top triple clamp. If the lower clamp doesn't look aligned with the top one, then that's the first thing to fix. They may be able to get twisted just a little with straight tubes, but usually mis-aligned triple clamps are due to bent top tubes. You'll have to disassemble them like you did for the fork seal swap, then roll the upper tubes on a known flat surface like a sheet of glass. With that mileage its probably not likely you have a damaged bushing, but if you rule out the first two possibilities then while you have the forks apart to check the upper tubes for bends you can put in a new set of bushings and cover that possibility too.
 
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paulcb

paulcb

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Thanks for the input guys. I need to clarify that this doesn't happen every time. I checked it on my commute home this afternoon, full stop about 7-8 times, never stayed compressed. It does seem a little "sticky" though... not sure it returns all the way every time. Also, in my garage, I can pull it up manually and it goes back down but not sure it goes back down as far as it should.

I checked the forks and they were both round, i.e. ?1.612" in both axes. I also looked at the upper and lower clamps and they appear to be aligned. I've not hit any curbs or potholes.

When I did the fork seals, the bushings looked good... plenty of bronze left, no silver showing through. Also, after assembly and before installing the forks, they "seemed" smooth and responsive when compressing manually, although I couldn't really compress them very well with my hands.

Anything I've missed? Am I just being too sensitive about this? Like I said, it seems to ride and handle just fine, although would like to compare it to another bike... maybe at the next RTE... any volunteers? ;)
 

John OoSTerhuis

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the bushings looked good... plenty of bronze left, no silver showing through
All the ST1100 fork tube and slider bushings' contact surfaces I've seen were coated with gray Teflon. The Honda Common Service Manual spec is to replace them "... if the teflon is worn so that the copper surface [underneath] appears on more than 3/4 of the entire surface."

Is your anti-dive working properly? During my last fork seals R&R I found part of the anti-dive plunger lip/seal in the bottom of the slider after separating the fork tube from it. Might something like that be blocking suspension fluid orifices...? Just thinking out loud here....

John
 
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Hey Paul,

1. they shouldn't be sticking at all, they should operate smoothly all the time.
2. I don't think the tube roundness is of any consequence over the part of the upper tube that's accessible with the forks still on the bike, I think they can be bent at or near the lower tube level and you may not be able to measure any distortion. Not sure how much you'd be able to measure even if you did measure right at a small bend, so I wouldn't put too much faith in that measurement.
3. take them off the bike and remove the springs, then compress/return them full travel with no springs and you should be able to feel if there's any binding or not. If you can't feel any binding at that point, then it will likely remain a mystery.
4. as John says take a close look at the anti-dive mechanism, both on and off the bike to make sure something isn't hung up there.
 

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My bet is on worn bushings though... ;-) Their regularly neglected items...
I replace them like every 36 to 42.000km (22.5~26Kmiles...)

The w/shop manual also lists the wear limits on the length of uncompressed fork springs, but I'd be highly astonished that their "hammered down" on a '01 with only 53K on it...
 
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paulcb

paulcb

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When I did the fork seals, the bushings looked good... plenty of bronze left, no silver showing through.
All the ST1100 fork tube and slider bushings' contact surfaces I've seen were coated with gray Teflon.
I got the colors wrong on my earlier comment about bushings. I carefully inspected each one and I remember now that there was no copper showing through the Teflon on any of them.

Looks like I'll need to pull the forks off again, check the bushings and anti-dive and verify sliding operation without the springs (thanks for that tip). I'll also measure the tubes for roundness. I believe the bushings to be good but I'm guessing they're pretty cheap to replace. Should be able to use the seals and dust boots I just replaced as long as protect them when sliding them off the tube?

I was leaning towards sagging springs but both of them and at only 53K miles? Any other thoughts?
 

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I'd replace all wear parts when already having them apart...
You'll be kicking yourself if a seal starts to seep only 2 weeks after the job...
 
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Anti-dive valves tends to be neglected/forgotton when installing new fork seals, etc.
Secondly, not THAT many miles on them, but the damening orfices tend to get ever so slightly enlarged over time from the oil friction(common on way older bikes). With 83K on mine now, I went to 10w Silcolene which definitely improved the dampening and reduced stationary 'sag';).
 
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All the ST1100 fork tube and slider bushings' contact surfaces I've seen were coated with gray Teflon. The Honda Common Service Manual spec is to replace them "... if the teflon is worn so that the copper surface [underneath] appears on more than 3/4 of the entire surface."

John
Concur with John. A certain amount of stiction is normal, but it sounds like what you have is excessive. RaceTech says ( 10-20 ) mm of stiction is normal. When I rebuilt my forks and installed a RaceTech Gold Valve & Emulator kit ( and RaceTech springs ) @ 54K miles, I replaced the bushings even though the old bushings still looked OK ( still had the teflon coating ). If you can see brass on yours, they are toast, I believe. You may have other problems, too - like a slightly bent slider. And when you installed the new seals , did you lube the seal lips with fork seal lube to reduce the "stiction" ?

BTW, according the RaceTech's "Spring Calculator" , the stock springs are perfect for a rider weighing ZERO pounds !!

The stock setup has way too light springs and way too much damping, according to RaceTech. RaceTech's cure is to install heavier springs ( based on rider's weight ) and use the proper damping with their Gold Valve and Emulator Kit. They claim the results will be a "plush, but firm" ride. I'm happy with my setup.

They recommend 5W in the right ( Valve ) fork and 15W ( Emulator ) in the left fork. Of course, that's not a recommendation for the stock forks.

The Gold Valve is installed in the right fork ( replaces the stock valve in the right fork ). And the Emulator is installed in the left fork ( and the anti-dive parts are removed because they are not necessary with the Emulator ). RaceTech also doesn't believe in progressive springs , because it's harder to set-up the front end properly with them - the spring pre-load affects the "static operating point ".
 
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ST1100Y

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BTW, according the RaceTech's "Spring Calculator", the stock springs are perfect for a rider weighing ZERO pounds !!
Well, they do intend to sell their product, so... frankly spoken... ;-)

If you're a not too ambitious rider and prefer a comfy set-up, the OEM suspension isn't bad at all... I rode the crap out of it for years...
If you want it a little firmer on braking and turn entrance, a change to 10W oil does fine...

Sure can all and everything be "tweaked"... by throwing money at it...
The crux is that the ST1100 is officially rated for a total payload of ~190kg/~420lbs... a bit too low for the real world...
Did some quick math and found my touring-ready, 2-up payload in the 250kg/550lbs range though... dunno what you guys haul along...
And this was the reason I'd opted for the Hyperpro/Wilbers upgrade front and rear...
Wouldn't like to miss it when on the road with two up, but I do have to accept that its quite firmer with a slight decrease of comfort when solo with no luggage...
Its really precise and generally total fun to ride, but our frost beaten roads do "call through" now...
 
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RaceTech is a very reputable company. I read their "Suspension Bible" book a few years ago, and they definitely know their stuff.

The suspension on the ST1100 is old technology. The Gold Valve & Emulator kit is definitely an upgrade and the install cost me only about $225, since I installed the kit myself. A lot of bang-for-the buck, IMHO.
 
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