USD Forks

You will probably need longer pre-load tubes (Zed1015 will be the man to answer this as it was his mod)

I think I’m doing your mod Wookie, where you just add the couplers to the top just under the fork cap. Doing it at the bottom like Zed did is slick, but more complicated than I think I’m set up for. 

With the damper rod extensions you can gain 32mm in length.
This does not affect pre load or spring tension in any way and no other mods are needed.
All they do is allow the stanction and attached axle clamp to protrude 32mm further out of the sliders.
You may wish to add an additional 32mm of fork oil to each leg but i have found no noticable difference using the stock amount.

Thanks Zed, I'm picking up what you're putting down. For my needs I won't need to go the full 32mm allowable, I think I only need about 20mm, but I will double check my math before I make any spacers. The complicated bit is just fork disassembly/reassembly in the first place. 

Stereordinary wrote:

Doing it at the bottom like Zed did is slick, but more complicated than I think I’m set up for. 

I'm finally making some progress on this. I bought a spring compressor tool (cheap one off ebay), a fork cartridge holding tool (from RaceTech), and a damper rod puller (Kawasaki OEM off ebay). With those I got one fork disassembled and able to understand a bit better how things work. I think ultimately Zed's method of lengthening the forks at the bottom is the way to go. Especially since I had to take everything apart to replace seals anyway.

It took me a fair bit of time to measure things out and get some idea of how the oil flows through the system. I still don't get much, I mean suspension is basically black magic as far as I'm concerned. But at least I can see how the spacer needs to be made. Here's some screenshots of the 3D model, any feedback would be appreciated.

Only one question, I assume that the spacer needs to be made of steel, or stainless steel, right? Aluminum seems like it would risk threads snapping at the base on the upper male-threaded part. 

Yes! Steel.

As for my opinion, you don´t need any extra front fork lenght extention.
My stock ZX9-R fork and brake parts upgrades are perfect for cornering and high speed drive perfomance and give me
enough ground clearance in any situation.....

 
 
 
 
 


 

Scirocco wrote:

As for my opinion, you don´t need any extra front fork lenght extention.
My stock ZX9-R fork and brake parts upgrades are perfect for cornering and high speed drive perfomance and give me
enough ground clearance in any situation.....
 

I appreciate the input, and your bike looks great, but ZX9R forks are well known to be longer than most all other sport bike USD forks. I'm quite sure that they are longer than my ZX6R forks. Here's a photo of one next to a ZXR250 fork, which I think is about the same length as my forks. 

The RWU ZX9 forks I am using are 30mm longer than the ZX6 version that use the same lowers. Even the ZX9 are 45mm shorter than a Stock “J” which uses a 19 inch wheel so without extensions I would be approx 70mm lower than stock with a 17 inch which would be a little to “public schoolboy” for my vision ( nose down, arse up)

Thinking out loud about the fork extensions again, but I’m wondering if it would be a good idea to use a thread locker on the male part of the extension as it threads into the cartridge. My concern would be in later servicing of the fork if while attempting to remove the lower banjo bolt, the cartridge might unthread from the extension first, and then I’d have no way of holding the extension. Thoughts? 

Stereordinary wrote:

Thinking out loud about the fork extensions again, but I’m wondering if it would be a good idea to use a thread locker on the male part of the extension as it threads into the cartridge. My concern would be in later servicing of the fork if while attempting to remove the lower banjo bolt, the cartridge might unthread from the extension first, and then I’d have no way of holding the extension. Thoughts? 

Agree with you completely, leaving them behind would be a PITA. Is there room to make the extensions from "hexagonal" bar stock (like I used for my kick stand adjuster) that way you could hold it with a long extension and deep socket if "the worst" happened ?

I was thinking the same thing. It certainly wouldn’t be hard to design it as a hex, so I might as well. Still, there wouldn’t be a problem with using a little thread locker as long as I apply it carefully, and give it time to set up before adding fork oil, right?