Fork overhaul

Bike is '92 ST1100 ABS. I apologize ahead of time because I know the topic has been beaten to death, but I've read through a bunch of threads already and feel like I'm more confused now than I was to begin with.

I just bought the bike last week, has 73,000 miles, and the front end is in desperate need of an overhaul. Right fork leg is leaking, so in addition to new seals, I figured I'd go ahead and throw in some new springs, oil and bushings while I'm at it. Seems like there are so many options, and I really want to buy the right stuff the first time around.

Here is what I'm after: I'm about 165lb without gear, will very rarely ride two-up, looking for a decent compromise between a comfortable ride for commuting on the freeway, but still stiff enough to handle the occasional twisties adequately. This bike is not my "canyon carver" - got another bike for that. Oh yeah, and I'd prefer to keep the cost on the budget side.

Really would prefer to buy everything I might need at one time so my downtime is limited. Already have a new front tire on the way. Can you guys help me with my shopping list?

See if a Sealmate would cure your leak. If not, from your description it sounds like the OEM setup might be all you really need, maybe up the suspension fluid from 5wt to 10wt. JMO I suspect that you'll not need new upper or lower bushings but they're cheap. Might as well also order the lower fork bolts as insurance if the old ones have to be drilled out.

edit: fork seal R&R tips (ST1100 AOW): http://www.st-riders.net/index.php?topic=907.0
STOC loaner fork seals R&R tool kit (must register): http://www.st-riders.net/index.php?topic=983.0

Regards, John

John OoSTerhuis said:

from your description it sounds like the OEM setup might be all you really need

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Should I not at least get a set of $70 Progressive springs? Those would probably be cheaper than OEM springs, and a little better performance, right?

Thanks for the tech link, awesome!

1.2kg sonicsprings from their .com site would be my choice.
I bottomed out my front end all the time before I put in the 1.2kg springs in the front.
I weighed about 20lbs more than you.
I used the 10wt John suggests and was very pleased (and have been ever since) with the front ends change...

Climbingaz said:

Should I not at least get a set of $70 Progressive springs? Those would probably be cheaper than OEM springs, and a little better performance, right?

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Hello __?__,

You certainly can install a set of aftermarket fork springs and heavier fluid, your choice. I'm happy with my PS springs and a Superbrace forkbrace. From a replacement standpoint, I suspect that your OEM springs are well within spec yet... are you having suspension problems other than the fluid leak? BTW, here's the link to the little Sealmate tool that might fix your leak: http://sealmate.net/ [a good tool to have onboard in the aux tool kit]

BTW, at that mileage your rear shock is quite probably in need of replacement. If you're having driveability problems, fixing/upgrading just the front end may not solve it as both ends need to be working properly.

John

Works also make progressive springs for the ST1100. While you are in there, changing out the springs is not that a big of deal other than the expense of the springs. You will have to sort out how much pre-load you want (the length of the spacer that most springs add in the tube).

Should have known I was going to get varying opinions since suspension set-up is so subjective. Thank you all for your input. I decided to place on order for a set of Sonic 1.10kg/mm springs. And I'll try some 10wt fluid. Now I'm trying to finish up my shopping with all the little extras, but I'm a little confused at what parts to get looking at the Honda microfiche:

http://www.mrcycles.com/fiche_section_detail.asp?section=158708&category=MOTORCYCLES&make=HONDA&year=1992&fveh=3682

I think I need 2 of part number 51490-MN8-305 SEAL SET, FR. FORK - which I think includes the fork seal and dust seal.

I'm unsure on the bushings....I think I need 2 each of part numbers 51414-KCR-003 BUSH, GUIDE and 51415-KCR-003 BUSH, SLIDER.

And I think I need 2 of part number 90116-383-721 BOLT, SOCKET (8X27) just in case I round out the old ones on disassembly.

Does that sound about right? Have I got the correct part numbers, anything else I might want to throw into the order? Thanks so much!!

Climbingaz said:

Should have known I was going to get varying opinions since suspension set-up is so subjective. Thank you all for your input. I decided to place on order for a set of Sonic 1.10kg/mm springs. And I'll try some 10wt fluid. Now I'm trying to finish up my shopping with all the little extras, but I'm a little confused at what parts to get looking at the Honda microfiche:

http://www.mrcycles.com/fiche_section_detail.asp?section=158708&category=MOTORCYCLES&make=HONDA&year=1992&fveh=3682

I think I need 2 of part number 51490-MN8-305 SEAL SET, FR. FORK - which I think includes the fork seal and dust seal.

I'm unsure on the bushings....I think I need 2 each of part numbers 51414-KCR-003 BUSH, GUIDE and 51415-KCR-003 BUSH, SLIDER.

And I think I need 2 of part number 90116-383-721 BOLT, SOCKET (8X27) just in case I round out the old ones on disassembly.

Does that sound about right? Have I got the correct part numbers, anything else I might want to throw into the order? Thanks so much!!

Click to expand...

Haven't read the tutorials here, but thought I'd mention one thing in case it hasn't be touched upon. The hex bolts at the bottom of the fork tubes require a longer than average hex bit driver. It needs to be long enough to go through an access hole on the bottom of the leg, then reach across the axle opening to the bolt head. I made one by cutting off a regular allen wrench and driving it with a socket. My bike is non-ABS, so ABS might be slightly different. Unfortunately, its been a while so I can't recall the exact size of the hex driver, but I want to say 8mm.

Would someone mind taking a quick look at my part number shopping list in post #7? Just want to make sure I'm ordering the correct parts. Thanks in advance!

Climbingaz said:

Would someone mind taking a quick look at my part number shopping list in post #7? Just want to make sure I'm ordering the correct parts. Thanks in advance!

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It looks correct to me, with a couple of comments.

1. the dust seals are generally reusable, so rather than pay $44 for the pair of dust seals and fork oil seals, you should be able to find just the oil seals for something like $10-15 a pair through any generic aftermarket supplier. I've never used factory seals on any bike I've owned, and usually get 50k miles out of a set of generic seals. Unless the dust seals are visibly damaged, just reuse the old ones.

2. the 8x27 bolts are unnecessary, IMO. Since the bolt threads sit in oil, the chances of damaging them are nil. The worst that will happen is they spin and won't break loose without using air tools to drive them, but I wouldn't worry about damaging them. I think mine have always broken loose with a hand ratchet the couple of times I've changed them.

Hi John, I have a problem with a clunking sound when I go over some bumps.
Doesnt do anything when I bounce on the suspension. Have you any ideas please?
Regards Kev

Dixiegambler said:

Hi John, I have a problem with a clunking sound when I go over some bumps.
Doesnt do anything when I bounce on the suspension. Have you any ideas please?
Regards Kev

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Hard to say for sure without actually hearing the 'clunk', but there's an anti-dive valve in the bottom of the left fork that makes a clunking noise when activated, that may be what you're hearing, and its normal.

Do you wear earplugs?

Stock suspension? Fresh suspension fluid? Last time the forks were apart?

I have a 2002 ST1100 non ABS and I bought Sonic 1.2kg springs and 7 wt oil. I pulled the fork caps off and found the right one attached to something. How/what do I do next? I am only replacing the springs, the seals are fine. My bike bottoms out after putting the stock 5w oil in. The forks never moved with the heavy oil that was in there when I bought the bike. I am trying to get this done this weekend because I take off for Utah/Arizona/Nevada after next weekend. Any help would be greatly appreciated.

Ben, it sounds like you need a service manual...

The right fork cap is attached to the damper rod. Hold the nut under it with a 14mm wrench and unscrew the cap with a 17mm hex-bit socket or allen. Then use a tool like one of these (in the STOC loaner Fork Seals R&R Tool Kits):



to hold the rod up while you compress the OEM fork spring and remove the Spring Seat STopper, releasing the spring.

Assume the forks are pulled to do a proper suspension fluid R&R with an ATF flush and dump x 3.

John

John OoSTerhuis said:

Ben, it sounds like you need a service manual...

The right fork cap is attached to the damper rod. Hold the nut under it with a 14mm wrench and unscrew the cap with a 17mm hex-bit socket or allen. Then use a tool like one of these (in the STOC loaner Fork Seals R&R Tool Kits):



to hold the rod up while you compress the OEM fork spring and remove the Spring Seat STopper, releasing the spring.

Assume the forks are pulled to do a proper suspension fluid R&R with an ATF flush and dump x 3.

John

Click to expand...

John,

I have the forks apart and the stopper off the damper rod and I have new sonic springs in and pvc cut to length, now my dilemma is to compress the spring so I can put the spring seat stopper back on. What do I use to compress the spring with to enable me to put it back on?

Sandwich the spring between a coupla wrenches and push down while a helper holds the damper rod extended and slips in the stopper. Fill the forks to the spec'd fluid level first, springs out, tube compressed.

Thank you so much. That did the trick. And my muscle bound 14 yo son. We got it in with a hanger holding th rod up.

Well, I rebuild the forks with the Sonic 1.1 springs, new bushings, seals, etc., but now I'm running into some issues getting the correct amount of sag. First go around, I obviously cut the spacers too long, causing way too much preload. I'm trying to get about 30mm of sag with me on the bike. Can anyone give me some ballpark guestimates on how much preload would accomplish my 30mm sag target? I'm about 165 pounds and again using the 1.1 springs. Bike is a '92 1100 ABS, Thanks!!

Climbingaz said:

Well, I rebuild the forks with the Sonic 1.1 springs, new bushings, seals, etc., but now I'm running into some issues getting the correct amount of sag. First go around, I obviously cut the spacers too long, causing way too much preload. I'm trying to get about 30mm of sag with me on the bike. Can anyone give me some ballpark guestimates on how much preload would accomplish my 30mm sag target? I'm about 165 pounds and again using the 1.1 springs. Bike is a '92 1100 ABS, Thanks!!

Click to expand...

maybe I haven't thought this through, but as long as you get some compression in the forks with the current spacers, the difference between the sag you have now and 30mm sag, is the amount you want to shorten the spacers. I think whatever preload you apply through the spacer length, translates into that much less upper slider travel to reach equilibrium. If you add 10mm to the spacer length, the upper slider now has to move 10mm less to support the weight of the bike by compressing the spring, and your ride height goes up by 10mm.

edit: this assumes you change the spacer length in each fork by the same amount, and don't just change one of them, but I think that's fairly obvious.