1996 ST1100 (Non-ABS) Fork Spring Spacers / Preload

[saturnaal]

Greetings ST1100 owners - can anyone provide the left and ride side fork spring spacer/preload collar measurements for an OEM '96 ST1100? Length is the one I need most, internal and external diameter would be helpful as well. More details for those interested:

I am currently in the process of rescuing a 1996 ST1100 (Non-ABS). The bike has about 70,000 miles on it, and narrowly avoided the scrapyard after the prior owner attempted to turn it into a 'cafe racer' of sorts without much success. The rear suspension was completely dead, so I ordered a replacement from Hyperpro along with a set of new fork springs. Upon disassembly of the forks, I discovered the springs inside appear to have been replaced with springs significantly longer than OEM or the Hyperpro replacements, measuring ~431mm. The right side fork lacks a preload spacer entirely, while the left side spacer is crudely cut from thin-wall tube and is shorter than OEM at ~82mm. There was very little preload compression when I disassembled, maybe a quarter inch or so tops. The fork oil was absolutely rank and very dirty, so they've been in there a while. Adding to the confusion, the new Hyperpro replacements measure around ~393mm, shorter than the 415.6mm quoted for OEM in the Clymer manual I have.

At this point I'm a little stuck on how to proceed. I was able to find an OEM right spring collar (Part#51402-MS2-003), but the left side collar (Part#51402-MT3-611) was unavailable. If anyone can provide the correct measurement for that part I'd be greatful. The documentation that came with the Hyperpro says to use the 'standard' spacer @ 130mm for left, 50mm for right. Furthermore, as this particular bike is going to end up substantially lighter than stock given how much of it is missing, I suspect I'll need to shorten each spacer anyway to decrease preload to get the suspension dynamics right. That will likely require some experimentation, so I'm planning to start full size and trim them as needed. If anyone has suggestions for how much to trim them buy per reduced weight, that would also be helpful information.

Additionally, the Clymer manual calls for Honda SS-7 suspension fluid which as far as I can tell is 5w? While the fluid Hyperpro provided with their kit is SAE 20. I'm unsure on what weight fork oil I should really be using here, especially with the bike being dozens of lbs lighter.

Thanks!

Current springs (both sides): ~431mm
Current left spacer: ~82mm
Spring free length quoted in Clymer manual: ~415.6mm
Hyperpro springs (both sides): ~393mm
Hyperpro left spacer measurement: 130mm
Hyperpro right spacer measurement: 50mm

 

[ST1100Y]

Looks like the Hyperpro linear progressive springs... offering smooth, yet precise handling...
I can't recall if mine were/are that significantly longer... used the OEM spacers though...
Found the suggested 20W oil plain impossible, a 10W still too harsh on the wrists and ended with BelRay 7W (which you'll have to seek in the MotoCross sections)...
Can't help with spacer length though as my '00's forks are back together (new bottoms installed), should have inquired 2 weeks ago...

 

[dwalby]

The first comment I'd make on this topic is there's no right/wrong answer. Everybody has a different body weight, gear weight, accessories added to the bike, and riding style so what's right for one person is totally wrong for someone else. Given that, I'll confirm some of your data above. Your Hyperpro provided measurements of 130mm left and 50mm right are correct, those are the stock spacer lengths. The stock fork oil SS-7 is 5W.

The easy part is adjusting the preload spacers, get a length of 1" PVC and cut your own in various lengths. Because the right spacer is a bit more work to replace than the left spacer, do all the adjustments on the left, it takes very little time to swap them out. What length you end up liking the best is impossible to predict, everyone is different, so asking for a preferred length is meaningless. BTW, that thin walled metal tube is the stock spacer, and it was cut down from its 130mm original length. I'd set that aside and use the PVC spacers on both sides. Another variable is the spring rate of the Hyperpro springs, how do they compare to the stock springs? Since Honda doesn't spec the spring rate of the OEM, that requires a bit of guesswork there.

For the oil 20W sounds way too heavy to me, and I prefer a sporty ride. Over the years I've used straight 10W, 15W, and blended 10/15W which is what I have now. I found 15W to be too harsh/stiff, so I can't imagine using 20W. I've never tried it, but someone here has experimented with different weight oil in each fork, since the damping mechanisms are different, and claims that to be a good setup. I can't recall the details, but you may be able to find it with a search.

So, just take a wild guess for the initial setup and take it from there. I'd suggest going with 10W oil as a starting point since its about in the middle range. With fresh oil if you don't like the response of 10W you can drain it out and mix it 50/50 with either 5W or 15W to get something a bit softer or firmer depending on which way you want to go. With a little luck you'll like 10W and not need to change it.

 

[saturnaal]

Thank you for your perspectives ST1100Y and dwalby - knowing that there is quite a bit of room for variation and preference here eases my mind somewhat about getting it 'right'. I'll just have to get them back together, along with the rest of the bike, so I can take it on a test ride and go from there. Before that I'll need to give them a decent cleaning to get the rest of the muck out of them. I'll pick up some 10w from the local shop to have on hand. Fortunately, the fork seals themselves seem to be in good shape. They must have been replaced when the forks were previously apart.

Looking forward to getting it back on the road - quite a bit of work left to do to get it into a state I'm confident in. In the meantime at least I have my CB1100EX to keep me entertained

 

[John OoSTerhuis]

Sounds and looks like you have the Progressive Suspension fork springs setup. BTDT, Honda SS8 (10W). The right OEM spacer (Spring Collar) is removed and the left one is shortened to 3.25” (or PVC tubing). Why don’t you replace the suspension fluid with 10W and try that first. BTW, use the manual’s fluid LEVEL specs, that’s what PS said and it has worked for me for years/100K+.

edit: while you’re at it, pull the anti-dive and inspect it. The piston in mine had a chip out of the seal and wasn’t seating/sealing properly.
edit2: what’s the ‘cafe racer’ look like? Pics?

John

 

[saturnaal]

Sounds and looks like you have the Progressive Suspension fork springs setup. BTDT, Honda SS8 (10W). The right OEM spacer (Spring Collar) is removed and the left one is shortened to 3.25” (or PVC tubing). Why don’t you replace the suspension fluid with 10W and try that first. BTW, use the manual’s fluid LEVEL specs, that’s what PS said and it has worked for me for years/100K+.

edit: while you’re at it, pull the anti-dive and inspect it. The piston in mine had a chip out of the seal and wasn’t seating/sealing properly.
edit2: what’s the ‘cafe racer’ look like? Pics?

John

I think you're likely right about the springs I pulled out being the ones offered by 'Progressive Suspension', based on the length and how it's currently set up. I'm likely going to replace them with the Hyperpro ones I have now, if for no other reason than that I don't trust anything done by the prior owner after what I've found working on it so far. I will pick up some Honda SS8 from the local dealer though.

Thanks for the tip about the anti-dive - I certainly plan to open that up to clean and inspect while I'm at it, so far everything I take apart yields new surprises, going to be as thorough as possible at this point.

I attached a picture of the bike in it's current partially disassembled state to the OP - but here's one of what it looked like when I picked it up. After a quick wash, even. As bad as it looks, I swear it was even worse in person. I couldn't quite capture the true horror of the thing in a photo.



While it started, ran, and all the lights worked that's about all I can say for it. Clutch master and slave cylinders were dry and non-functional, with seals either installed incorrectly or outright missing. I rebuilt and bled that first to make sure it could roll under its own power. A short test ride revealed an excruciatingly unsettling ride - the rear shock was completely blown, the tires were rock hard, there was noticeable drivetrain lash, and it just felt off in all kinds of ways. That very poorly installed 'pan-seat' didn't help matters. One side of the exhaust was capped off with a plumbing plug, with a hollowed out and shorted Whites Bros (or knockoff) on the remaining side making it very loud. The wiring harness is a disaster. Too much to list really - I'm working my way through it one bit at a time as a winter project.

Here's a few more to give you an idea of the state I'm trying to bring it back from - hopefully into something that will be genuinely enjoyable to ride.