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That Fighter Guy
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Discussion Starter #1 (Edited)
Hey guys and gals, I thought I'd do a how-to on taking apart/dismantling inverted forks. What I have here are stock forks off of an 07/08 ZX6R, but they are all constructed very similarly. If you can take them apart, then you can put them back together (hopefully). If you need certain specs like spring length and whatnot, be sure to check your service manual for those. Ok, on with the how-to. Please read the whole thing before getting started. There are different steps that need to be followed for oil-only change or oil and fork seal change. Fork oil only does not require the internals to come out of the fork. Full disassembly to remove the bad seals requires the bottom allen bolt to be removed (look up at the fork while on the bike and you'll see it---typically a 10 mm allen/hex key).

With the forks still on the bike and wheel removed there are a few things to do first.

1) Loosen the preload adjuster (counter-clockwise)
2) Loosen the rebound adjuster --OR--
3) Tighten the rebound adjuster (full clockwise)
4) Loosen the fork cap about one turn (you'll unscrew it the rest of the way after the fork is removed--triple tree helps hold the fork steady while you pop that cap loose).

If you go with method (2), then you need to make sure the nut on the damping rod holder goes back where you found it. This is the nut that the cap screws down against. If your cap is either too far down or too high on that damping rod holder it will screw up your suspension settings, namely the rebound damping. Before you remove the cap after the spring is compressed you can measure or eyeball where the nut is, then make sure it is there when you put it back together. Your service manual will also tell you how far down that nut is as measured from the top of the damping rod holder.

If you go with option (3), screw the damping adjuster full clockwise until it stops (don't crank down on this!). Now when you screw the cap back down on top of the damping rod holder the cap will stop when the damping rod hits bottom. In this case you will turn the nut on the damping rod holder until it contacts the bottom of the cap, then simply tighten it against the cap. There, no damping issues to follow. This is a good method to use after a fork rebuild or fluid change to better ensure both forks are set up the same. I'm sure method (2), per the manual, works fine, but if you go with method (3) you don't have to worry about forgetting where that damn nut was set before loosening it. I know I get engrossed in stuff at times and forget where something was before I started.

I did mine with a vice because these forks were intended to go on the bike, but I discovered they were bent, so I dug deeper to see how bad they were.



Don't forget the compression damping adjuster at the bottom of the fork (optional for oil change only).



With an appropriately sized socket, unscrew the cap. Be sure to use good counter torque as to not slip and round off your cap. Not only is it ugly, but it's out in the open and you will hate yourself every time you look down. :lol:



This is what you'll see after the cap is loosened and the outer fork leg is pressed all the way down.




With some spare parts sitting around along with a ratchet strap, I made a fork spring compressor (saved myself $120). Connect the fork spring compressor tool to the spring spacer (see the holes?) and compress the spring to reveal two nuts butted up against each other, and insert your fork rod holder thingy under the nut to hold it in place. (the fork is being held in place by my bench vice, ratchet strap running through the caliper mount).




With two wrenches, loosen the cap from the damping rod, remove it, and set it aside on a clean surface.





Measure the height here so that you can put that nut back in the same spot. I spoke earlier with the other method to ensure this stays correct (damping adjuster fully clockwise).


Now drain the fork into an appropriate container as best as you can. Pump the damping rod holder and outer tube while inverted and draining.



Remove the dust seal and oil seal retaining spring.




Using a slide hammer motion, grasp the inner and outer tubes and pull them apart. It'll take a few good smacks.

With a thin flat head screwdriver, you can remove the two bushings. Make sure you inspect the bushings for damage. If they're damaged, replace them. These have a teflon coating on them. If it's severly damaged, replace it. Damage can also be seen if you have silver discoloration in your fork oil after it's drained in the pan.



Here's the lower bushing, as you can see it's damaged, which is likely due to the previous owner wrecking the bike and damaging the forks.



Put an allen key or socket into the bottom of the fork and remove the bolt. More often than not, the bolt wants to loosend up, but then not come all the way out and leave the internals assembly spinning. What I did was insert a small piece of wood into the fork leg to wedge between the assembly and fork tube to give it enough resistance to get that stupid bolt out. If you have an impact driver, then you can do this without the ghetto stick. It's even easier if you zap this bolt out with an impact or allen wrench (better yet a hex bit on a socket/impact) while the forks are still on the bike; the fork spring pressure helps keep the internals from turning.




Paint stir stick as my wedge.




With that nut out, the internals will come right out and you're done. Now you can take a stick and rag and thoroughly clean the tubes and check for straightness (on a known flat surface or run-out gauge). A simple wooden dowel from an arts and crafts store works beautifully. Cram a rag in the fork tube, then use the down to move it around and push it back out. Dump a small amount of clean oil in the tube to help remove any more residue present.

I hope this helps someone out. Take care. :thumbup:
 

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That Fighter Guy
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15,175 Posts
Discussion Starter #3 (Edited)
how much off were the bent forks?
This much.



The fork in the back isn't as bad as the other one. It has a straight outer tube and slightly bent (2 mm maybe I'd guess) inner/lower tube. I rolled them on my straight bench, so my measurements aren't perfect, but they are accurate in the sense of BENT or NOT BENT.
 

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If I were to just change my fork oil would I only need to do up to the part where you compressed the fork springs? Btw, nice write up and thorough pictures, I can never document the stuff I do.. not patient enough to take pics lol
 

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That Fighter Guy
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Discussion Starter #5
If I were to just change my fork oil would I only need to do up to the part where you compressed the fork springs? Btw, nice write up and thorough pictures, I can never document the stuff I do.. not patient enough to take pics lol
Compress the spring, remove the cap, invert the fork, and pump as much old fluid out as you can. The rod that the cap is screwed to needs to be pumped as well as the tube itself to get the most oil out as possible.

After all the old stuff is out, you have two options:
1) pour in the appropriate amount of oil back in with a measuring cup, or
2) use a fork oil level gauge to get the oil to the appropriate level.

Your owner's manual will give you both the oil height (tubes compressed, without spring) and the oil volume. If you're not tuning the forks for track use (I.e. putting a different oil level in the forks than the factory specifies to change fork performance) then you can go with the measuring cup method and be perfectly fine. Oil level gauge costs about $30 and isn't hard to use so long as you have an extra pair of hands or a vice to hold the fork upright when sucking out the excess fluid with the gauge. I used the measuring cup method for my last oil change and the bike performed well on a track day as well as the street.
 

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That Fighter Guy
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Discussion Starter #7
Impressive stuff Larry.
Thanks, buddy. Can you believe all I did was read the manual and went for it? LOL. I decided to take pics while I was at it and figured it might help someone out in the future.

Turns out the manual is very wrong where it tells you to simply remove the lower allen bolt from the fork. That made me a little irritated when it just spun after it was broken free. LOL. Nothing I couldn't handle though.

I'm thinking about changing out the fluid in my forks this winter, so I may do a whole nother thread with just that task specifically. The fluid was put in last December, but I've already gone like 11,000 miles on it, so it may need a change. Plus, it's the winter, what the hell else am I going to do on my time off of work? :thumbup:
 

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you dont need to measure the rebound threads, u simply tighten your rebound completely in before disassembly, then when u screw the fork cap back on it will stop when the rod bottoms out, then tighten it up

and i have tested capacity vs oil level, and capacity is at minimum 20mm short with all different forks from honda kawi suzuki ect.. so i highly suggest never using a measuring cup.. always go with oil height gauge tool.

also, a lot of people dont bleed the outter tube, it is very important that u pump that fork with ur hand covering the top tube before measuring fork oil height.


and as for damper holding tool, i use a long ass phillups screw driver and my cordless impact, only fork ive delt with that the cordless impact isnt enough for is 05+ r1's. It helps to remove the damper rod bolt first after u simply loosened the fork cap..

and one last note, all 10w fork oil is different from one manufacture to the next..

i've rebuilt about 100 sets of forks.. and i road race which taught me a shit load about suspension
 

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That Fighter Guy
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Discussion Starter #9 (Edited)
I've always read to screw the rebound out all the way before dismantling, also the preload. If you use your method then you don't need to measure the rod holder, which I've not thought of. If you take the rebound OUT and then not set the rod height right, then you'll fuck up your rebound adjustability.

Long story short, there's more than one way to skin a cat. I normally go by fork level rather than volume, but either method for a street bike will work fine.

EDIT: OP updated to reflect both methods of making sure the cap goes back down to the correct level.
 

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you dont need to measure the rebound threads, u simply tighten your rebound completely in before disassembly, then when u screw the fork cap back on it will stop when the rod bottoms out, then tighten it up
I was going to say this too, I screw the rebound adjuster all the way in before doing anythign to the fork for disassembly. Then take it all apart do what you need to do then when putting the cap back on the fork you screw it it until it just stops spinning freely, you want that rebound adjuster to just barely bottom out, then tighten up the fork cap and you'll be good to go :)
 

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That Fighter Guy
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Discussion Starter #11
Good to know. I'll have to remember that next time I have to do this. The mechanics behind it make sense. I've just read everywhere else to back out all the adjusters before disassembly.

Note: This thread wasn't meant to be all inclusive, but to give people an idea of what to expect before they tackle the job.
 

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Note: This thread wasn't meant to be all inclusive, but to give people an idea of what to expect before they tackle the job.
I forgot to throw you rep and kudos, but this how-to along with the factory service manual helped me replace my fork seals. Since I have the 05/06 zx6r, (those pictured are 07/08 right?) I had to make a little bit different fork spring compressor tool. Other than that, everything else worked and I now have perfect forks that perform flawlessly.
 

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That Fighter Guy
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Discussion Starter #13
A bit of a late reply, but I'm glad to hear all the pics I took and posted went to good use. :thumbup:
 

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Hi guys, sorry to resurrect the thread but I had one question that I'm sure someone might know.

Why did the OP suggest removing the lower allen bolt in order to remove the cylinder assembly? Was this just because he intended to do a full disassembly to check the straightness of the components?

In other words, for a fork seal/bushing/dust seal replacement I will not need to remove the internals correct? I imagine the OP had access to every seal and bushing once he separated the inner and outer tubes.


Thanks in advance! I really appreciate it :D
btw, first time posting here. I come from zx6r forums and stt forums.
 

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That Fighter Guy
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Discussion Starter #15
Yes this was for full disassembly. In order to replace blown seals and bushings you need to pull the "guts" out so that you can separate the inner and outer fork tubes to remove and replace the seals and bushings. If you're just trying to get away with an oil change, then you don't have to do all of this. However, if you're draining the oil and you get a dark silver color with the oil, that's a bushing gone bad that needs replaced (teflon warn off). From my experience, the bushings tend to go bad if you've had a leaking seal for a while. The oil escapes the tubes and the blown seal allows contaminants into the forks which wears away the teflon on the bushings and ultimately wears away at other parts if left unattended for too long.
 
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