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:
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
Oil drain pan
Fork seal grease
500 ml graduated cylinder
Fork oil level adjuster
For seals, you need:
Small flathead screwdriver
Fork seal driver
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.