ST1100 Fork Oil change - How to?

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Interesting thread as I am preparing to rebuild the forks on my '01 ST1100A with 57,000 miles on it. I have all of the new parts, i.e o-rings, bushings, seals, etc. (all OEM) and I am going to order new Race Tech fork springs. I can remove the forks from the bike and probably get them apart myself, and I will have a very accomplished motorcycle mechanic to assist me with putting them back together, thankfully! My intention is to thoroughly clean and flush them prior to reassembly.

I am going to use Race Tech .90kg springs, I think. I had the forks on my '98 built several years ago with the .95kg springs and they were a little stiffer than I like. That rebuild included Race Tech Gold Valves and Emulators and the bike handled great. I also had the same set-up installed on my 2008 Wing (during a brief period of incoherence, when I traded an ST1100A for a Wing--what a mistake!). I am not going with the Gold Valve set-up this time on this ST; I don't know that I could tell the difference.

What nominal weight is the original Honda fork oil? I think I read somewhere that it is quite thin, like maybe 5 wt. I think I will use 7.5 weight as a compromise for control and smoothness.

Where does the 17mm Allen deal come into play?

Any suggestions, cautions, guidance, advice, or criticisms are welcome.

Thanks!
 

John OoSTerhuis

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My suggestions etc are above. The 17mm hex-bit socket is used on the standard models' fork caps; also the early ABS models. Your later ABS II model's caps take a 24mm socket.

John
 
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Thanks John,

I kept looking at my fork caps, and at the instructions in the Haynes manual, and knew they were not 17mm and I could not figure out all of the emphasis on a 17mm socket. All of the guidance from this site, based on years of experience from long-term owners such as yourself, is invaluable for owners of ST1100s. Heck, I remember reading your advice when I got my first ST, a '95, a feeeeew years ago!

Ride safe!

Steve
 
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Old thread but, I was wondering if it matters what I flush the forks with? Specifically, I have some type F ATF fluid on the shelf, can I use that or does it need to be dextron/mercon? This is just for the flush, I have SS-7 for the final fill up.
 

Sunday Rider

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Old thread but, I was wondering if it matters what I flush the forks with? Specifically, I have some type F ATF fluid on the shelf, can I use that or does it need to be dextron/mercon? This is just for the flush, I have SS-7 for the final fill up.
I used tranny fluid as well. I don't think it matters what kind, just as long as you let it drain properly overnight as mcthorogood said.
 
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I completed the flush and dump X 3 today and my forks are currently hanging like bats from the workbench letting the last of the ATF work its way out. I found something very interesting during the flushing process. The drain plug on the Left fork (non cartridge, with anti-dive) goes to a blind hole! I don't know if its a manufacturing defect, or what but its not drilled all the way through. The other fork plug does, and it really helped during the cleaning process. Has anyone else seen or heard of this?
 
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snip ........ I found something very interesting during the flushing process. The drain plug on the Left fork (non cartridge, with anti-dive) goes to a blind hole! I don't know if its a manufacturing defect, or what but its not drilled all the way through. The other fork plug does, and it really helped during the cleaning process. Has anyone else seen or heard of this?
Sure about that ? Maybe it's completely clogged up with "gunk". Try twisting a small phillips screwdriver tip in the hole and see if you can dislodge any junk.
 
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Sure about that ? Maybe it's completely clogged up with "gunk". Try twisting a small phillips screwdriver tip in the hole and see if you can dislodge any junk.
I didn't want to go nuts on it if it really was a blind hole. I poked at it a little but it is rock hard. The other fork drain was completely clear and both forks oil didn't look as awful as I expected, not to the point that it should cause that much of a clog.
 
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I didn't want to go nuts on it if it really was a blind hole. I poked at it a little but it is rock hard. The other fork drain was completely clear and both forks oil didn't look as awful as I expected, not to the point that it should cause that much of a clog.
perhaps the PO sheared off the small bolt that plugs the hole, and inserted a shorter one as a replacement.
 
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perhaps the PO sheared off the small bolt that plugs the hole, and inserted a shorter one as a replacement.
The bottom of the hole is perfectly smooth, not jagged as a snapped fastener would appear. The left and right fork drain plugs are the same size.
 

Sunday Rider

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Wow, never heard of this before. This must have been the one fork with permanent fork oil!;)

I wold be tempted to drill it, but since you've done the draining and cleaning, why bother.

When I changed the oil in mine, I remember the right fork oil smelled putrid, and the left one was pristine.

Good luck solving this mystery.
 
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Wow, never heard of this before. This must have been the one fork with permanent fork oil!;)

I wold be tempted to drill it, but since you've done the draining and cleaning, why bother.

When I changed the oil in mine, I remember the right fork oil smelled putrid, and the left one was pristine.

Good luck solving this mystery.
You came to the same conclusion that I did. The perfectionist in me wanted to drill it out but I had already finished the flushing process and I would've had to flush it again to insure I got all the drill shavings out. Luckily flushed out that fork first, so I didn't know how much easier that little drain makes it to get all the fluid out.
 
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The bottom of the hole is perfectly smooth, not jagged as a snapped fastener would appear. The left and right fork drain plugs are the same size.
very odd indeed, if it was never drilled I'm surprised that when they tapped the threads into it that the tap didn't leave any machining marks on the bottom of the hole. Also, the drain plug is sized to work with a thru hole, does the bolt head fit flush on the circumference of the drain port? Since the oil can't escape anyway, the bolt position is irrelevant. There should also be a small flat washer to take up some space, that is normal. If the washer has any appreciable thickness to it then that might explain how the regular size bolt was used.
 
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very odd indeed, if it was never drilled I'm surprised that when they tapped the threads into it that the tap didn't leave any machining marks on the bottom of the hole. Also, the drain plug is sized to work with a thru hole, does the bolt head fit flush on the circumference of the drain port? Since the oil can't escape anyway, the bolt position is irrelevant. There should also be a small flat washer to take up some space, that is normal. If the washer has any appreciable thickness to it then that might explain how the regular size bolt was used.
The two drain bolts from the two forks are identical from size to the matching washers (copper?). the bolts snug down the same on both forks.
 
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Alright, Alright... you win! None of this made any sense to me either so I decided to go take another look at the suspect drain hole. It still looked as sealed as ever. The bottom of the hole looked to have the same black texture as the outside of the lower forks. It's sealed alright...but what if? So I found a nail and stuck it in the hole and pushed...HARD... and POP! Through it went. So, Mr. Dwalby, thank you sir for solving this mystery... I would've just buttoned it all up tomorrow and never thought about it again until next time, which most likely wouldve been worse with more grime built up.
 

John OoSTerhuis

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I could be all wet here, but take your anti-dive apart and see if a piece of the piston lip hasn't broken off. BTDT During a fork seals R&R I found a piece of mine down at the bottom of the fork slider when I got it separated from the fork tube. N.B.

John
via iPhone 4S
 
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Alright, Alright... you win! None of this made any sense to me either so I decided to go take another look at the suspect drain hole. It still looked as sealed as ever. The bottom of the hole looked to have the same black texture as the outside of the lower forks. It's sealed alright...but what if? So I found a nail and stuck it in the hole and pushed...HARD... and POP! Through it went. So, Mr. Dwalby, thank you sir for solving this mystery... I would've just buttoned it all up tomorrow and never thought about it again until next time, which most likely wouldve been worse with more grime built up.

Darn it, you've ruined my plan to fly out there in the name of automotive research. I was willing to tour various KY establishments to accumulate a variety of alcohol based solvents that could have been used in an attempt to dissolve the offending gunk. Glad you got it back to normal.
 
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I could be all wet here, but take your anti-dive apart and see if a piece of the piston lip hasn't broken off. BTDT During a fork seals R&R I found a piece of mine down at the bottom of the fork slider when I got it separated from the fork tube. N.B.

John
via iPhone 4S
John, your never all wet when it comes to ST1100 knowledge! I have already inspected the anti-dive and all is well. Thanks for the tip.
 
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