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HOW TO: Fork oil & seal change

183K views 270 replies 73 participants last post by  Victorh97 
#1 · (Edited)
It seems many people are surprised that you're supposed to change your fork oil, some are even surprised there's oil in there. Well, there is, and you're supposed to change it. Fork oil breaks down just like motor oil and becomes shit. I do it yearly for track riding, you can get away with every other year on the street. You'll need all the tools required for front wheel and fairing removal, including a front triple tree stand. This will take about 2-4 hours depending on experience.

For just oil, you need:
6mm Allen
30mm socket or wrench
17mm open-ended wrench
Fork compressor tool
Damper rod holder
8mm Allen (needs to be 4 inches or more)
Cartridge holder tool
Gloves
Oil drain pan
Fork oil
Fork seal grease
500 ml graduated cylinder
Fork oil level adjuster

For seals, you need:
Small flathead screwdriver
Fork seal driver
New seals

If you don't have a fork compressor tool, I can almost guarantee you'll mess up your forks. Forks are much more expensive than the tools. Either buy the tools, borrow them from a friend, or take your bike to a shop. I've got all the tools to do this in Bellevue, WA and I'm happy to help (for a small fee, of course).

DISCLAIMER: I'm not a mechanic. If you mess up your forks, you probably did something wrong and it's not my fault. You should never have to muscle anything apart. If something isn't coming apart or together fairly easy, you're doing it wrong and you should stop.

This was done on my 09 Daytona. 06-08 (and most inverted forks for that matter) have the same procedure.

Start by removing the front wheel. Taking the side fairings off will make the job easier but it's not necessary.



Remove the brake calipers from the forks. Steel brake lines are less delicate than rubber, but I still like to hang them by bungee cords rather than just let them dangle.



Loosen the top triple clamp bolt and the clip-on bolt with the 6mm allen. Leave the bottom ones for now.



Measure the distance the fork protrudes from the top triple clamp. When you put the fork back in, you want it to be the same distance. Also take note of your rebound settings as you'll need to change them on reassembly.



Loosen the top cap on the fork by 2 or 3 turns with the 30mm socket.



While supporting the bottom of the fork, loosen the lower triple tree bolts. It should slide down fairly easily, if not just wiggle it back and forth as you gently pull down. Back out the top cap the rest of the way while holding the outer (gold) tube, then slowly slide it down.





Now you need the fork compressor tool. This one's a RaceTech:



The white PVC pipe that's now exposed has 2 holes on either side of it. The compressor tool's pegs slide into these holes. Tighten the bolt by hand.



Spin the nut at the top to compress the fork spring. Keep going until you can no longer use one finger to spin the wrench. You can do some damage if you use a giant breaker bar to tighten it down as far as it'll possibly go.



You should now have a partially exposed locknut. It's under the top cap inside the tube.



Pull the top cap up to expose it more, put the 17mm wrench around the lock nut and loosen it as you hold the top cap with the 30mm socket.



Once the lock nut is loose, unscrew the cap by hand. You should also put the fork in an oil drain pan, it gets messy. If you remove the lock nut, put it back the same way, it's directional. Threads are on top.



The spring will come right out. Take note which end faces up and set it aside.



Dump the oil into your drain pan. Remember, this bike isn't even a year old and the oil already looks like this. It smells like it looks.



If you want to be lazy about it, you can call it job done, fill it up with oil and put everything back together. If you want to get all the old crappy oil out, you need to drain it from the bottom too. Slide the outer tube off the inner tube. Mine was easy, slightly older forks may need to be convinced apart. You can put the bottom of the fork in a soft vice and yank the outer tube off. Don't use any tools to pry the tubes apart.



Look at the bottom of the inner tube assembly and you'll see a hole with an Allen bolt inside.



Gently tighten a soft vice around the inner tube. It only needs to be tight enough not to fall out. Place the drain pan under the tube.



Now you need the cartridge holder tool. If you don't have one, it's not that big of a deal, just skip this part and leave the little bit of crappy oil at the bottom.



Gently lower the tool into the inner tube and rotate until you feel the notches engage with the cartridge.



Slide the 8mm Allen through the hole to the bolt. Grab the cartridge holder and loosen the Allen. Having a friend to hold the holder is helpful.



This bolt comes out and the rest of your shitty oil drains. There should be a copper washer on the bolt - don't lose it.



You can either hold the tube upside down and gently let the cartridge come out, or you can use this damper rod holder



Screw on the holder just a couple threads and lift out the cartridge



This is the cartridge. This is what Ohlins charges $1500 or however much it is. Give the rod a few pumps to get all the fluid out.



If you're not doing seals, reassemble. If you're changing them, set aside all the inner tube parts and move on to the outer. If you don't have a fork seal driver, don't bother trying without it. A screwdriver won't work. We have 41mm forks so you need a 41mm driver. This one's from RaceTech:



The black rubber thing at the bottom of the outer tube isn't your fork oil seal; it's a dust seal. You should usually replace it when you do the oil seal too, but I'm cheap so I'm going to reuse it. If you have a new one, do whatever you want to get it off short of using a dremel. I gently used a small flathead screwdriver to pry it off, carefully not damaging it.



You'll see a black lock ring next. Use the flathead to gently coax it out.



Now we're to the oil seal. If you remove this, 99.99% of the time you need to replace it with a new one, or it'll leak. Put a rag on the tube so you don't scratch it and use the flathead on the bottom of the seal. Gently pry upwards on the seal, carefully not scratching anything inside except the seal. Work your way around the seal prying a bit at a time until it comes out. Take note of which side of the seal was facing up. If you put the new one in backwards, it will leak.



At the very bottom is a washer. Remove and save.



Your tube should be free of scratches, like this:



Out of the following parts, you need to save the lock ring and the washer. The oil seal will be replaced so you can throw the old one away along with its little springs. I'm keeping the dust seal.



Grease the inside and outside faces of the oil seal and the inside face of the dust seal. Slide the dust seal, lock ring, oil seal and washer onto the inner tube, in that order. Make sure the oil seal is facing the right way.



Slide the outer tube onto the inner, then slide the washer and oil seal down into the outer tube. Leave the dust seal and lock ring out of the way.



Put the seal driver below the lock ring and dust seal and slide it down onto the oil seal. You don't need to slam it hard, but you need to slide it down firmly to make sure the seal seats.



Hit the seal until you expose the groove for the lock ring.



Put the lock ring in by hand, then make sure it's in the groove with the screwdriver, being careful to scratch neither the tube nor the new seal.



Press the dust seal in firmly until it's flush with the tube.



Reassemble the inner tube by slowly dropping in the cartridge, holding it with the holder tool and screwing the Allen with washer back in the bottom. Torque to 24 nm. Now we're going to refill with oil. I use 5w synthetic RaceTech or Motul. It comes in a 1 liter bottle, so pour out a little less than half into the graduated cylinder.



Slowly pour it all in. Screw on the damper rod holder and pump the piston about a dozen times to make sure the air bubbles are out.



You can leave the damper rod in as you'll need it later, but I took it out to make adjusting the oil height easier. Adjust the level of the oil with the oil level adjuster. This RaceTech one has a telescoping needle that makes it easy to set the height. The 06-08 manual says the fork oil needs to be 72mm from the top of the inner tube without a spring, but apparently Dave Moss recommends 110 mm, so that's what I'm going with. Measure the needle with a ruler to make sure it's the proper length.



Set it on the rim of the inner tube and suck the fluid out until it's 110 mm (or 72mm if you want to follow the manual) from the top.





Slide the spring back in, making sure it's in the same direction as before. The smaller diameter end faces up.



Screw the damper rod holder back on, then set the PVC tube with its metal cap on top of the spring. Put the fork in the compressor tool again and carefully compress. Hold the PVC centered as you compress so it doesn't fly out.



Pull up on the damper rod holder until you see the locknut again.



Set the rebound adjuster (flathead screw on top of the fork cap) all the way to soft seat, then go in 3 and a half complete turns (1260 degrees). Unscrew the holder while holding onto the rod, then screw the fork cap back on until it stops.



Back off rebound all the way. Tighten the locknut back onto the cap. There is a torque value but I couldn't get a torque wrench to fit. I just went as tight as I could get it with one finger.



Loosen the compressor tool and grease the cap's threads and O-ring with some seal grease. Tighten the cap by hand.



Slide the tube back in, making sure it sticks out same distance as before. Tighten bottom triple tree bolts to 25 nm. Next, top cap to 25 nm. Finally, top triple tree bolt to 20 nm and clip-on bolt to 27 nm. Put the rebound setting same as before. That fork's done, same process goes for the other one.

 

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#42 · (Edited)
based on this thread, I also changed to 5w fork oil, increased the air gap, and dropped the forks flush with the tripples a couple of weeks ago. WOW, did it make a tremendous amount of difference! I honestly was so fustrated with the bike that I didnt even want to ride it. The front end was very harsh and non compliant. I could not ride it hard if the road was anything less than perfect. It literally felt like the forks were locking up, and just skipping over the bumps. But now, while still not perfect, its a completely different bike, and very ride-able at a fast street pace. I can actually hit a bump mid corner, and the forks actually absorb the bump instead of skipping over the bump. Plus the forks being dropped adds a little bit of stability as well. At this point, I have not adjusted anything, I put all the clickers back in the middle of their range and just went. I know I need to add a click or two of rebound, but overall its ready to go.

Dave Moss recommended 110mm, and T-man recommended 120mm air gap, so I went with 115. Basically the air gap acts like another spring inside of the sealed fork. You can compress the air slightly, but with only 72mm, it wont compress much, and you get very stiff at bottom the bottom of the stroke. The larger air gap makes it more plush and compliant at the bottom of the stroke.

For reference, I have a zip tie on my lower leg to help visualize how much stroke I am using. Before changing the air gap and fork oil, the zip tie would only go down to like 24mm above casting, and the fork was stopping, like it was hitting hard bottom. Now, the zip tie is moving down into the 16mm range. this means I am using about 8mm more travel in the fork, and its not a hard bottom, its firm, but not hard.


BTW: You HAVE to have the fork cartridge compressor tool with these forks! I have done many forks in the past, and was able to be creative and use ratcheting straps and other tools to pull the cartridges apart. Not with these forks. The holes in the pre load spacer are too far down or something, and the top out spring is absurd. I had to stop in the middle of my project and order the damn $120 tool, and even then with the tool, I had a hell of a time getting to the nut that connects the fork cap to the rod.
 
#43 ·
BTW: You HAVE to have the fork cartridge compressor tool with these forks! I have done many forks in the past, and was able to be creative and use ratcheting straps and other tools to pull the cartridges apart. Not with these forks. The holes in the pre load spacer are too far down or something, and the top out spring is absurd. I had to stop in the middle of my project and order the damn $120 tool, and even then with the tool, I had a hell of a time getting to the nut that connects the fork cap to the rod.
Yeah, I really wasn't kidding about that part :laugh:

Glad to hear they feel better!
 
#46 ·
7.5w is stock, and it was entirely too stiff for me, and we hit 90-100* on a regular basis here during the summer. I could not even imagine how stiff the valving would be if you went with a heavier weight.
 
#47 ·
Another thing to consider is that fork oil weight ratings are rarely accurate. One brands 5w can be the same as another brands 10w and vice versa. I typically find that if a manufacturer or suspension builder recommends a specific weight it's best to use the brand they are using otherwise the results are not guaranteed.
 
#51 ·
Nice write up. I was able to remove the cap without the special tool, but it was pretty bubbafied.

The manual mentions 13mm of thread should be exposed above the lock nut prior to reassembly, but you dont reference that. It seems that length could drastically impact rebound adjustment by changing the position of the internal rod relative to the adjusting screw on the cap. No?
 
#52 ·
Nice write up. I was able to remove the cap without the special tool, but it was pretty bubbafied.

The manual mentions 13mm of thread should be exposed above the lock nut prior to reassembly, but you dont reference that. It seems that length could drastically impact rebound adjustment by changing the position of the internal rod relative to the adjusting screw on the cap. No?
That length will drastically impact rebound if you don't make it the same, and I did reference that. I don't measure it by thread though, I measure it by rebound. It's one of the last steps of reassembly:

"Set the rebound adjuster (flathead screw on top of the fork cap) all the way to soft seat, then go in 3 and a half complete turns (1260 degrees). Unscrew the holder while holding onto the rod, then screw the fork cap back on until it stops"
 
#57 ·
I would think the style of riding and/or road conditions on which you ride would impact the life of the oil.

I initially assembled my forks with the service manual's recomendation of 13mm thread showing. I ended up with 3.5 turns of adjustment on one fork, and just under 3 turns on the other. I disassembled them (on the bike) and found both still had 13mm showing. Reassembled them using the method described here and now they are both the same, 3.5 turns of adjustment. I also have a much faster rebound setting full out using this method compared to using the service manual specs. I believe The fork that was just under 3 turns was not fully releasing the damping rod.
 
#61 ·
So I watched Dave Moss' video on how to change fork oil (http://www.onthethrottle.com/edownloads/) and it seems to conflict with the approach recommended on this thread. The key differences being that he did not use a fork compressor tool as he did not remove any of the internals, he just opened the top up and drained out the oil. He also refilled it based on volume (measuring what came out and putting the same amount back in).

Is this approach compatible with our bikes at all?
I realize it seems like a less perfect way; but from my limited understanding it seems like it would work.
 
#62 ·
Dave's method will work on our bikes if just changing the fork oil, the only issue with the volume measuring method that Dave recommends is that we are also discussing changing the total volume of the oil to effect the air gap. So, if you were just doing a straight oil change, with no changing of air gap, then yes, Dave's method can work, with out much hassle at all.

If you were to dump the oil, and replace it with exactly the same amount that came out(which is still only an approximation, because there will still be some left in the internals) then your air gap would remain the same. Most of us are changing the air gap from the factory 72mm to 110mm(115personally). How much volume of fork oil do you remove to get the bigger air gap? Its only a guess if you cant measure it correctly.

The only proper way to measure an air gap is to remove the cap, preload spacer, and spring, and then measure how far from the top of the tube to the fork oil for the air gap you want.
 
#65 ·
I tried using that exact same kit on my '10 Triumph, by myself, and I couldnt get the spring to compress enough. Just not enough hands and enough force. Actually I even had my wife come out and try to slide the flat bar under the spacer if I could get the spring down far enough, and I never could.

I ended up buying the spring compressor stand for $100
 
#68 ·
#71 ·
That is true but I need the tool maybe one time in 2/3 years or something. If you change forks often I agree that the compressor tool in the start post is the best option. But for me the two handled compressors are good.
I can spent the 100$ for fuel :)

Someone made one for me, works perfect :thumbup:

 
#72 ·
I had to re-do the seal on one fork this weekend (ended up doing an fork oil change on both, though).... I had no idea about having to compress the spring, so I wasn't prepared for that. I ended up with a make-shift spring compressor. I was able to fabricate up a braket and used my floor jack to compress it all. It took a few hours to get it all figured out and fabricated up, but once it was done, the second fork went like a breeze.

I also made a little extractor tool with a piece of stainliness tubing and M10x1.00 nut to reach down and grab the piston rod.

I had everything except the nut, so it only cost my $0.75, and got everything done between Sat night and Sunday afternoon.

I also went with the 110 mm fluid depth, instead of the stock 72 mm level, as was suggested, but I don't do any track time (yet), so I'm sure it will be hard to discern a difference.

Anyway, thanks for the good info!


 
#74 ·
ha! That's the first decent home-made compressor I've seen, nice job dude. Saved yourself $150!
Looks like my next project. Our garage has a huge wooden beam and I have a spare scissor jack. would be perfect for this.
 
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