USD Forks

It is not unironic that I took a photo of upside down forks while they were upside down, lol. 

Anyway, my plan is a methodical one. I hope to carefully measure and 3D model nearly every millimeter of this entire front end, as well as the necessary parts of my bike’s stock front end, and use all of that to create a custom axle, and at least the top triple, but possibly both top and bottom triples. Then I will have to have those parts machined, and I’m sure that won’t be cheap. 

Yay, fun! 

I have "re-worked" stock ZX6R stem to fit the longer ZX9R forks to my 82 1000Ltd. Custom tree's are nice but there are cheaper options

Well , nice forks you got!

I also had to mahcined the stem shaft but i kept the triple tree and all the rest from the donnator front end.
And i order the riser clip-on from Woodcraft Racing, the stock clip-on were nearly hitting the tank and i wanted them to stand higher.

Picture is the cutaway view of the shaft and the other part assembly.


 

I’m thinking I can maybe press out the original Zephyr stem to reuse, and I have a lower triple that is supposed to be from a ZXR250 I can check and see if it fits the forks. If that works out, the axle and upper triple are the only parts I’ll need to have custom made. I can save myself some money by designing and 3D modeling them myself, it’s just the cost of having them machined. 

Riser clip-ons is a great solution, but I’m determined to keep my original handlebars. 

Stereordinary wrote:

I’m thinking I can maybe press out the original Zephyr stem to reuse, and I have a lower triple that is supposed to be from a ZXR250 I can check and see if it fits the forks. If that works out, the axle and upper triple are the only parts I’ll need to have custom made. I can save myself some money by designing and 3D modeling them myself, it’s just the cost of having them machined. 

Riser clip-ons is a great solution, but I’m determined to keep my original handlebars. 








 

It is entirely up to you how you go about this but from experience you are best to use as many parts as possible that are designed to work together. Why do want to use the ZRX triple? What you are doing is very similar to the conversion I have just done and you are in danger of over complicating things. Your stock bearings are - upper 25x47x15 (same as my 1000Ltd) lower is 28x52x16.5 (also same as mine) the process I followed was

1. press out ZX6R stem
2. Check top bearing retaining nut thread is no bigger than 25mm
3. machine stem down to 25mm for top bearing (the earlier stem for RWU forks is 25mm as standard)
4. Machine stem down to 28mm for lower bearing (you may need to reduce the shoulder under the bottom bearing if you are a little short on length)
5. Fit stock Zephyr bearings

this way you are using all OE parts that are made to work together (just modified) I chose to press a stainless insert into the bottom of the stem to reinforce the area around the bottom bearing that had been reduced. You can then use "bolt on" risers to fit your stock handlebars (or a bolt on "super bike" bar conversion). This way the only custom parts you need to worry about are an axle, calliper mounts and instrument mounting (there are two 6mm threaded holes in the top yolk for the locking bolts on the stock clip-ons) you also need to think about your speedo drive and steering stops

 
 
Just done a quick google search ref wheel bearings, it looks like yours are 42x15x13 and the ZX6R are 47x25x13. There are bearings available in the size you need (42x25x13) but you would need to check they are suitable for your intention or alternatively you could have the wheel machined out from 42mm to 47mm and use 6R bearings in your zephyr wheel which would then mean you can use the ZX6R. Axle

 

Whoa, ok now that’s interesting. I had thought about bearings and whether or not it was possible to use the stock ZX6R axle, but I just assumed it was a non-starter. That could be a great solution. 

The ZXR250 triple that I have has a lot of features that would be good for me, but I went and grabbed it from storage today, and it doesn’t fit the ZX6R forks. So that’s a no-go. Given all the variation in Kawi triples across all models, I’d be overjoyed if I could find one that works. But I have been searching around and not found one yet. 

Thanks for all the tips here, really giving me a lot to chew on. 

edit: Question, where are you finding information about what size bearings various bikes use? I went looking and thought it would easier, but not finding much.  

Stereordinary wrote:

Whoa, ok now that’s interesting. I had thought about bearings and whether or not it was possible to use the stock ZX6R axle, but I just assumed it was a non-starter. That could be a great solution. 

edit: Question, where are you finding information about what size bearings various bikes use? I went looking and thought it would easier, but not finding much.  

If you use the below link to identify bearing EG: 6302-2RS (Zephyr wheel bearing) then type the bearing number into google. WARNING: if you go the custom bearing route make sure the supplier confirms they are suitable for wheel bearings !!

Identifying the correct wheel bearing for Kawasaki bikes (bikebearingshop.co.uk)




 

I would suggest you do plenty research before buying any parts, I think I have found a problem with your plan to use the Zephyr front wheel - the 2004 ZX6R uses "radial mount" brakes which means adapting to the stock set up may not be possible 

 

Again, very helpful, thank you Wookie! 

Yes, the ZX6R uses radial mount calipers, but one of the reasons I picked that specific year was because they use the same diameter rotors (300mm) as my stock Zephyr rotors. I figure I might have to shim the rotors out, or replace them with a different offset rotors, but in theory it should still work. 

I already emailed one bearing manufacturer about if their bearing would be suitable for a wheel, and their answer was less than helpful. So I’ll keep looking. I do also like the idea of having the wheel machined for the ZX6R bearings as you suggested, but I have no idea where I could take it locally to have that done right, let alone what it would cost. Again, just keep searching I guess. 

If you shim the rotors make sure they are still located on the centre hub so they run true and don't shear the bolts

Again, good to know. I will look for correct offset rotors first. 

I think maybe something I could do that would be helpful is to spend an afternoon one of these days, and pull my wheel out, and just do a quick and dirty test fit with the forks to kinda get a better idea where things align. I can take measurements and tracings and add them to my 3D model. Wouldn’t be too hard, and I could put it all back together, and torque it to spec when I’m done. 

Would someone be able to look and give me suggestions about where I might be wrong on my geometry here? My manual says that the trail should be 104mm, but I have a gap indicating that I'm getting more trail than I should be.

I'm wondering if maybe the trail should be calculated with some amount of compression on the forks. In other words, fully extended I measured 775mm on the forks from axle center to top, but maybe when the full weight of the bike is loaded, the wheelbase is shortened to that 104mm trail number.

Or maybe I'm supposed to use the front wheel axle as the center of rotation to bring the rear wheel up so that both tires are flat to the same plane. This would angle the wheelbase center line slightly.