USD Forks

Wookie58 wrote:

As a regular contributor to the forum I see no issue with you reaching out to share the cost of this project.

Thank you!

Wookie58 wrote:

I assume a chunk of the cost is to write the CNC programmes ? have you thought about reaching out with a separate post to the membership (it's possible that one of the many engineers on the forum may possess the skills to write the programme and be prepared to help you out?)

I'm not sure what's the major cost, if it's a conversion from my file to a CAM program, or the materials and labor, etc. What I do know is that there are a couple of websites (including Xometry, and Cognito Moto) that I can upload my files and they provide an instant quote. I used Xometry to have the axle spacers made, but I'd love to be able to go with Cognito Moto for the triple trees, as they are US-based, already have familiarity with motorcycle triples, and their price for multiple units is actually better than Xometry. As far as help from members here is concerned, I'll take all that I can get, and hopefully there's some interest once I post up a thread in the for sale section.[/quote]

Wookie58 wrote:

With regards joining the two parts of the top yolk, you could consider the below...

I have certainly considered your idea here, and am still looking at it as a potential option. The only drawback I can see is that if I want to disassemble various parts involved later, pulling the bolts out will loosen the mounting of other components that wouldn't otherwise be loose. It could make some operations more complicated than they would be otherwise.

TexasKZ wrote:

The right adhesive would be plenty strong enough to hold the instrument cluster... the cost of such high tech adhesive may be prohibitive.

I can get West System epoxy from my local marine supplies store, and was thinking that might be sufficient. If not, I'm curious what would be a good choice. Perhaps a polyurethane glue? I wouldn't need a lot of it, so a small quantity might make it affordable.

TexasKZ wrote:

By the way, have you reached out to PDM Custom Fabrication?

I found their email address, but haven't reached out yet. Not quite sure what to ask exactly, but perhaps I should get the conversation started.

Based on my experience with them, I can add a couple more good reasons to go with Cognito. Their customer service is easy and attentive, and they make absolutely beautiful stuff.

zed1015 wrote:

Fork extensions for the damper rod.
Male thread at one end to screw into the damper,  female at the other to take the cap head bolt at the bottom of the leg , drilled through for the passage of the damping fluid and flats milled either side to take a spanner.

Aaaaand, we're back! I was thinking about using zed1015's method here for getting that extra 20mm's out of my forks. Looking at info and videos about fork disassembly (including the FSM for the forks I have) they all show starting at the top, but I have heard there is a method where you start at the bottom. Supposedly removing the large bolt at the bottom of the fork is a lot easier when you have the spring compressing the assembly. But then one source said something about that bolt breaking easily, which I can't imagine a bolt that large just snapping. So I'm trying to make sense of it all. Is there any reason why I couldn't start with the bolt at the bottom, and once that's removed, pull the cap off the top? The whole cartridge should come out as one piece right? Then I could add the extension piece at the bottom like zed did, and reassemble. I guess there's a question of getting the torque on that bolt right after reassembly, but wouldn't it be accurate if done with the fork bottom held steady in a vise?

Also zed, you mentioned drilling it through for passage of fluid, but I can't tell from your photos where. All the way through the center I guess? If it's just taking the place of the bottom bolt, which then threads into it, why does it need that passageway?

There is a special tool to hold the internals once the spring is removed, this will also hold it while you torque the bottom bolt on reassembly. Torque spec will be in the FSM as will the number for the holding tool (they aren't crazy expensive)

Stereordinary wrote:

 

Also zed, you mentioned drilling it through for passage of fluid, but I can't tell from your photos where. All the way through the center I guess? If it's just taking the place of the bottom bolt, which then threads into it, why does it need that passageway?

Yes! On forks with rebound damping the bottom bolt also resembles a banjo bolt which allows fork oil to pass through.
The extension also needs drilling through lengthways to allow a continuation of that passage.
 

Just thought I’d update where I’m at with this project. I was busy with other things for a while, and waiting to hear back from Cognito Moto. But I’ve had a little bit more free time, and a bike in my shed for other service, so I am turning my focus back to it. 

I decided to revisit Wookie’s suggestion of moving the forks in closer together to eliminate the need for any kind of rotor spacer. I had previously assumed that it would be too difficult to take the wheel in and out for tire changes. But then I thought, well how difficult are we talking, and is it still doable? So I moved the clamps in, making the fork-to-fork spacing 200mm. 



It works, and it doesn’t. In order for the calipers to center on the rotors, I still need to move each fork an additional 2mm in. Also, the largest section of the fork (where the lower triple clamps) is now touching the headlight bracket, and causing it to flex inward a little. The good news however, is that the wheel is actually very easy to get in and out because the right side spacer now just fits through the lower fork clamp. 

For the next revision I want to try moving the forks in that extra 2mm, but I also want to see if I can reduce the offset a little. This will do a few things, correcting the overall geometry, moving them away from the headlight bracket, and closing the gap between them and the fuel tank while turning full lock. Will keep y’all updated. 

With all of this narrowing of the fork spacing (5+2=7 each side) I'm looking at the spacers that are needed to adapt the ZX6R forks to the Zephyr axle.

Quick recap, for those not caught up on this thread: We previously discussed changing the bearings to fit the ZX6R axle into the stock Zephyr wheel, and/or having the Zephyr wheel milled out to accept a ZX6R bearing. However I've just hit nothing but brick walls with both of those ideas. Bearing manufacturers don't want to say their bearings are sufficient for the job, and no one seems to want to mill a wheel (if there even is enough space). Plus there's the added complication of my preference for using the stock speedo drive. So unless some other answer comes up on those topics, I'm going to be making axle spacers. 

Here is a screen grab of what the spacers look like (in yellow):


The fork lower is represented in a gold/orange color, and the Zephyr axle is the light purple. 

My concern with this is that the spacer needs to be shorter than the total width of the fork lower by 7mm. A few mils and I probably wouldn't worry about it, but as you can see, it's sort of floating above one of the fork lower pinch bolts. I could make it the full length, but then I'd need to also make a separate inner spacer instead of using the stock one, and I highly doubt it would work at all like that on the other side where the speedo drive is. 



So the question is whether or not it's ok to set it up like this. That inner fork lower pinch bolt is only clamping against so much material, but maybe that's ok? It does sit over the centerline of the bolt. Maybe I need to design a new inner spacer, and maybe the speedo drive can be modified? If it was milled flat on it's left-most side... (hard to explain in words)? 

Just did a speedo drive test fit. It was looking like there was no way the cable would fit around this fat Nissin caliper, so I decided to take a gamble and modify the drive itself. I thought that might be a smarter idea than trying to modify the fork lower. Basically all I did was remove the two notches on the drive that are there to help stabilize it in the stock fork lower. By the looks of it, with the cable attachment part angling outwards, and the brake caliper radial mounts angling inwards, they might overlap, which would stabilize the drive. Pretty pleased to report that it works. Unless anyone can see any reason why this is a bad idea, I've got it mounted in a functional manner. 

I would love some feedback on the posts above. Pretty please? 
I'm not an engineer, and I genuinely don't know if I'm creating a problem with this narrow spacing concept. The centerline of the forks is only about 0.75mm inside the centerline of the axle collars, so I feel like that's probably not a huge deal. But is it? Should I go back to the wider spacing and just shim the rotors?

Going back through this thread and revisiting old ideas. I still have yet to find a 42x25x13 bearing rated for motorcycle wheel use, but AllBalls does sell a bearing that is 42x25x9. I don’t know if it would work with a 4mm spacer behind it, and I think the spacer tube that sits between the wheel bearings would then also have to be 8mm longer. But I guess that might be an option. 

Additionally, I realized that in theory I could use a ZRX axle and speedometer drive if I was able to source the conversion bearing. Food for thought. 

I did a USD fork conversion last spring for my best friend and Harley Davidson enthusiast bike.
His 2004 FXDWG,had a spongy front brake and a poor performance/response behavior of the fork.This is the finished result.

before:

 

now:

 
 

and and my current non Kawasaki project: 

 
 
 
 

I’ve got a couple more questions about doing the fork extensions talked about previously in this thread. 

I understand how to do it, but I need to purchase if make a fork spring stopping tool, like this:


It seems simple enough to make, but does anyone know how wide the “slot” needs to be? I’m guessing somewhere around 10mm, but wondering if anyone knows off hand. 

My second question is about fork spring preload. With the tensions in place I think that means the springs are effectively longer within the forks, is that correct? So then that would make them softer, and therefore to compensate I would drive the preload adjuster in further, right? I think the standard setting for preload on my forks is 14mm out, but with 20mm extensions, am I going to be able to compress them enough?