Flushing Front Forks

Joined
Sep 10, 2011
Messages
2,211
Location
West Michigan
Bike
'98 ST1100
STOC #
8470
Have my forks out to flush & change the fork oil. Removed the top caps and poured out the two-year old fluid. I completely disassembled and cleaned the forks two years ago when I installed a RaceTech Gold Valve & Emulator kit.

Don't want or need to completely disassemble them again.

So, how do I flush out all the old fluid ? It looked pretty dark when I poured it out. Thinking about flushing with ATF. Read on another post that someone used MMO to flush with. Got some of that, too. Comments or recommendation, please ??
 

John OoSTerhuis

Life Is Good!
Joined
May 10, 2005
Messages
5,218
Location
Bettendorf, Iowa
Bike
1991 SSMST1100
STOC #
1058
Hi Jim. Half a quart of ATF, pump-n-dump x 3. If you have a standard model with little plugs on the fork sliders, leave a bit of ATF in at the end of the last cycle and pump the last bit out through those. Cover the end of the fork tube with your palm as you compress the tube. Then extend the fork tubes and leave the assemblies on their sides, slightly elevated, to drain overnight out of the plug holes. You may be surprised at what's in the last few drops of oil in the morning. HTH

Edit: take the opportunity to disassemble and inspect the anti-dive unit.

John
 
Last edited:
Joined
Mar 13, 2012
Messages
5,046
Location
soCal
Bike
'97 ST1100
STOC #
687
I always change my oil frequently so it doesn't get too dirty to begin with, not sure what 'pretty dark' means without seeing it. I usually just pump them a bunch of times with the bleed screws removed (non-ABS have these, I think the ABSII doesn't) and refill with clean oil. If I get really anal I'll turn them over for a half hour or so and see if anything drains out, but I'm usually not that careful, and I'm pretty sure the time(s) I did that nothing of any significance came out anyway. I figure I'm putting back ~500ml of oil, so if 5-10ml happens to get left behind that's 1-2% of the total volume (and there's probably not that much remaining in there anyway). I don't worry about having some old residual motor oil in the crankcase when I do an oil change, so I feel pretty much the same way with the forks.
 
Last edited:
Joined
Feb 27, 2011
Messages
3,357
Age
52
Location
Rindge, NH
Bike
2006 ST1300
Because whatever you put in there isn't going to completely come out, I would use what is supposed to be in there- get a couple quarts of the cheapest fork oil you can buy and flush with that. I use the same technique for engine oil when I buy vehicles that have been neglected. I do several quick oil changes with very cheap oil before the final change using my preferred oil.
 
Joined
Mar 13, 2012
Messages
5,046
Location
soCal
Bike
'97 ST1100
STOC #
687
I'm sure I'll be the odd man out on this one, but here's my question regarding flushing vs. not flushing. If there was any meaningful amount of crud left in the forks that didn't come out with normal pumping and draining, wouldn't you notice the next time you changed the oil that it was a little dirtier than the previous time, due to the accumulated crud. Since mine always looks the same at every change interval without flushing, I've never bothered.

Neglected/unknown is a different story, the OP just rebuilt the forks on the last oil change, so the condition is known.
 
OP
OP
Jim Van
Joined
Sep 10, 2011
Messages
2,211
Location
West Michigan
Bike
'98 ST1100
STOC #
8470
Hi Jim. Half a quart of ATF, pump-n-dump x 3. If you have a standard model with little plugs on the fork sliders, leave a bit of ATF in at the end of the last cycle and pump the last bit out through those. Cover the end of the fork tube with your palm as you compress the tube. Then extend the fork tubes and leave the assemblies on their sides, slightly elevated, to drain overnight out of the plug holes. You may be surprised at what's in the last few drops of oil in the morning. HTH

Edit: take the opportunity to disassemble and inspect the anti-dive unit.

John
Thanks everyone for your response, but after much deliberation, I think I will take John's recommendation - Pump-n-Dump x3 . Maybe on pump #2 , I will use some MMO, just for S&G's . And BTW John, with the RaceTech Gold Valve & Emulator kit , the internal anti-dive parts have been removed. RaceTech says it isn't needed with an emulator.

Looks like I need to pick up a few more quarts of ATF today.

On second thought, after the overnight drain as John suggested, I may do one last flush with the bottom drain plugs removed with some 10W fork oil I have left over. BTW, I will be using 5W in the right tube ( cartridge side ) and 15W in the left tube ( Emulator side ) , per RaceTech recommendations for the GV & Emulator kit , so I might as well use some of that old 10W for flushing.
 
Last edited:
Joined
Jun 3, 2006
Messages
3,512
Location
British Columbia
Bike
2021 RE Meteor 350
BTW, I will be using 5W in the right tube ( cartridge side ) and 15W in the left tube ( Emulator side ) , per RaceTech recommendations for the GV & Emulator kit , so I might as well use some of that old 10W for flushing.
Glad to hear that Race Tech confirms what was told to me by a suspension shop about using different weights in each fork, even with the OEM set up.
 
OP
OP
Jim Van
Joined
Sep 10, 2011
Messages
2,211
Location
West Michigan
Bike
'98 ST1100
STOC #
8470
Well , I got the forks flushed this afternoon, but it took awhile. After doing the pump-n-dump x3 , the ATF was still coming out grey. I wasn't making much progress. I has some Simple Green close by , so I filled each fork and pumped-n-dumped using the Simple Green and I could see that helped clean them out better. Then I gave them another pump-n-dump x1 using ATF. The ATF looked much cleaner after using the Simple Green. Then I did a pump-n-dump x1 using MMO and another pump-n-dump using ATF again. It was looking pretty clean coming out by then. Good thing I remembered I had a case of old FA-2 ATF in the barn to get rid of.

BTW, The cartridge side seemed much worse than the damper rod ( emulator ) side.

I then gave it a final flush with the 10W fork oil I had left over. I'm going to settle for what I see now - looking good.

I'll let the forks drain overnight with the drain plug removed.

After all this, I thought I was remiss by going as long as I have since I had the forks completely disassembled two years ago when I installed the RaceTech G.V. & Emulator kit , so I checked my Owner's Manual to see how often the fluid should be changed. No replacement interval listed, only inspection !!! Duh !!! From here forward, I will be flushing & changing yearly.
 
Last edited:
Joined
Mar 13, 2012
Messages
5,046
Location
soCal
Bike
'97 ST1100
STOC #
687
Jim, how many miles was it between oil changes? I usually change mine with every front tire, that way I know it will always be 8-10k miles.
 
Joined
Jun 3, 2006
Messages
3,512
Location
British Columbia
Bike
2021 RE Meteor 350
Jim, how many miles was it between oil changes? I usually change mine with every front tire, that way I know it will always be 8-10k miles.
That sounds a bit excessive to me. Especially if you use a synthetic fork fluid. Three years or 30,000 miles for me.
 
OP
OP
Jim Van
Joined
Sep 10, 2011
Messages
2,211
Location
West Michigan
Bike
'98 ST1100
STOC #
8470
Jim, how many miles was it between oil changes? I usually change mine with every front tire, that way I know it will always be 8-10k miles.
+1 . It's been almost exactly 20K miles. From now on, I'll be doing it every spring , along with a fuel filter change, since I'm a preventative maintenance fanatic and I don't want to waste too much ATF during the flushing procedure.
 
Last edited:
Joined
Mar 13, 2012
Messages
5,046
Location
soCal
Bike
'97 ST1100
STOC #
687
+1 . It's been almost exactly 20K miles. From now on, I'll be doing it every spring , along with a fuel filter change, since I'm a preventative maintenance fanatic and I don't want to waste too much ATF during the flushing procedure.
I think I waited 20k miles the first time when the bike was new, which was my typical interval on other bikes I'd owned prior to the ST. But for some reason I've never understood, the ST fork oil was very dirty at 20k, so that's when I dropped it to every front tire change. At 10k the ST oil looks like other bikes at 20k (or more). On my Triumph Daytona the fork oil looked brand new, it seemed like a waste to even change it, the original color was still bright and there was hardly any visible dirt suspended in it. To me a fork seal is a fork seal, so I don't know what it is about the ST that causes it to dirty the fork oil so much compared to other bikes I've owned.
 
OP
OP
Jim Van
Joined
Sep 10, 2011
Messages
2,211
Location
West Michigan
Bike
'98 ST1100
STOC #
8470
I think I waited 20k miles the first time when the bike was new, which was my typical interval on other bikes I'd owned prior to the ST. But for some reason I've never understood, the ST fork oil was very dirty at 20k, so that's when I dropped it to every front tire change. At 10k the ST oil looks like other bikes at 20k (or more). On my Triumph Daytona the fork oil looked brand new, it seemed like a waste to even change it, the original color was still bright and there was hardly any visible dirt suspended in it. To me a fork seal is a fork seal, so I don't know what it is about the ST that causes it to dirty the fork oil so much compared to other bikes I've owned.
Interesting !! But it is what it is, so every 10K ( basically every spring is my plan.

OK, Now for a new non-suspension question :

While I have the front forks off ( BTW, forks are re-filled and ready to go back on the triple-tree. Each fork took just under 16 oz. , so I enough 5W & 15W to do it again next spring ) , I'm planning on cleaning the clutch slave cylinder and replacing the seal ( just for S&G's since I'm a PM fanatic ). It seems to me if I don't remove the clutch rod ( assuming the oil seal is good ) , I shouldn't lose any motor oil.

Correct ??
 
Joined
Jun 3, 2006
Messages
3,512
Location
British Columbia
Bike
2021 RE Meteor 350
Interesting !! But it is what it is, so every 10K ( basically every spring is my plan.

OK, Now for a new non-suspension question :

While I have the front forks off ( BTW, forks are re-filled and ready to go back on the triple-tree. Each fork took just under 16 oz. , so I enough 5W & 15W to do it again next spring ) , I'm planning on cleaning the clutch slave cylinder and replacing the seal ( just for S&G's since I'm a PM fanatic ). It seems to me if I don't remove the clutch rod ( assuming the oil seal is good ) , I shouldn't lose any motor oil.

Correct ??
From the floor, measure the height of the oil level in the sight glass and compare that distance with the slave housing.
 
OP
OP
Jim Van
Joined
Sep 10, 2011
Messages
2,211
Location
West Michigan
Bike
'98 ST1100
STOC #
8470
OK, Now for a new non-suspension question :

While I have the front forks off ( BTW, forks are re-filled and ready to go back on the triple-tree. Each fork took just under 16 oz. , so I enough 5W & 15W to do it again next spring ) , I'm planning on cleaning the clutch slave cylinder and replacing the seal ( just for S&G's since I'm a PM fanatic ). It seems to me if I don't remove the clutch rod ( assuming the oil seal is good ) , I shouldn't lose any motor oil.

Correct ??
Feedback Info. : I took a chance and now I know theoretically, since the clutch rod passes through a seal in the front of the clutch cover, there should be no loss oil loss when removing the slave cylinder. And of course, I had to pull the clutch rod to replace that seal and to see how much oil I would lose - none. Maybe that is because I have the front forks off and a jack under the engine sump ( using a wooden block between the two ) and the front end is tilted up until the rear tire contacts the floor ( ?? ). So, clutch slave cylinder is now rebuilt and seals replaced. Time to move on to the timing belt and pulleys. These old ST1100's are easy to work on and parts are relatively cheap !!
 
Joined
Mar 13, 2012
Messages
5,046
Location
soCal
Bike
'97 ST1100
STOC #
687
Time to move on to the timing belt and pulleys. These old ST1100's are easy to work on and parts are relatively cheap !!
Wait until you price out the water pump, and the TB/pulleys are no bargain either. The Gates TB is the only reasonably priced thing under that front cover.
 

John OoSTerhuis

Life Is Good!
Joined
May 10, 2005
Messages
5,218
Location
Bettendorf, Iowa
Bike
1991 SSMST1100
STOC #
1058
Feedback Info. : I took a chance and now I know theoretically, since the clutch rod passes through a seal in the front of the clutch cover, there should be no loss oil loss when removing the slave cylinder. And of course, I had to pull the clutch rod to replace that seal and to see how much oil I would lose - none. Maybe that is because I have the front forks off and a jack under the engine sump ( using a wooden block between the two ) and the front end is tilted up until the rear tire contacts the floor ( ?? ). So, clutch slave cylinder is now rebuilt and seals replaced. Time to move on to the timing belt and pulleys. These old ST1100's are easy to work on and parts are relatively cheap !!
Pictures and part numbers, Jim? TIA

John
 
OP
OP
Jim Van
Joined
Sep 10, 2011
Messages
2,211
Location
West Michigan
Bike
'98 ST1100
STOC #
8470
Wait until you price out the water pump, and the TB/pulleys are no bargain either. The Gates TB is the only reasonably priced thing under that front cover.
I'm holding off on the water pump - I hear it should be good for another 40K miles. Even at $250, that's a heck of a lot less than a new or newer bike or even depreciation on a new or newer bike. However, I'm wondering if it is re-buildable ? I may contact an auto water pump re-builder to inquire about that.

As far as the pulleys go, I bought a used set and did some experimenting. I removed the grease seals ( not an easy task - soften first by using a heat gun ( gingerly ) and small screwdriver to pry the outside of the seal ). I flushed out all the old dirty blackened grease with brake clean, and then re-lubed. They felt like new when I was finished. Don't use too much grease - only a little more than a film is needed and too much could get slung out.
 
Last edited:
OP
OP
Jim Van
Joined
Sep 10, 2011
Messages
2,211
Location
West Michigan
Bike
'98 ST1100
STOC #
8470
Pictures and part numbers, Jim? TIA

John
Sorry John, no pics ( already re-installed ).

Clutch Slave Piston ( cup ) seal : 22865-MJ8-003 about $7
Clutch Slave Piston Rod Seal ( oil seal 8 x 18 x 5 ) 91209-MB0-003 about $3
Clutch Cover Rod Seal ( oil seal 8 x 25 x 8 ) 91204-MB0-013 about $3
Slave Cylinder Gasket 22862-MW7-650 about $3.50 , but I reused the old gasket. It stayed stuck to the Clutch cover in one piece and it still looked like new.
 
Top Bottom