KX500 hybrid suspension.

[cutting torch]

I'm building a '92 KX250 with a '94 (ish) KX500 engine. I am going to use the suspension from an '08 KLX450.

Since this bike will be about 40 pounds lighter than a KLX450, but I see myself jumping it much more than my own KLX450, I wonder if I should respring it, or leave the stock rates alone.

BTW, my KLX450 is stock, and is perfectly sprung for me, at 140 pounds. Odd, huh?

Any suggestions or ideas?

torch

[The Flyin Hawaiian]

I would ride it first before you change springs. The linkage ratio will be much differant from the KLX and any settings that work on the KLX most likely wont work with the 92 chassis, if the shock even fits. Try it and see. You can probably get the forks to work w/o too much trouble.

[cutting torch]

The forks will work. The head tube length is within the adjustment range of the triples, and both bikes use the same head bearings.

On the linkage ratio.... How is that determined? I would guess that it is wheel (axle) travel:shock travel.

I wonder whether that is a constant or progressive ratio, though.

Also, before I have even tried to fit the 450 shock, I have wondered if it is too long, and if a set of lowering links for the '92 would correct that and the ratio at the same time.......

I'm done wondering for now. If anyone has a smackdown for me, give it up! I'm not easily offended, and the smackdown will save me some time!

torch

[500HORZ]

ride it and worse case you may have to gain some weight or put rocks in your pockets

[ktmdude]

It should be good if you like a stiffer setup. You can put less fork oil and loosen the compression clickers for a softer front end. I would do what the others say and ride it and feel it out. I don't know what to tell you about the back side. Sorry. The bike sounds cool, I would like to check it out.

[don46]

I would almost guarantee you the shock is to long, I believe they are the same length as say a 250f new or old, and as such it will change the geometry. what you can do is depressurize the nitrogen and change the clevis, your 250/500 should be shorter but will still work you just have to be careful installing and make sure it is located on the shagft in the right place so  you have full adjustment for the rebound.

[cutting torch]

Don, it seems that you are one step ahead of me!

I tore down the 250 today to explore the shock fit, and there are a few issues. The 450 shock is 7/8" longer than the 250shock.



As you can see, the yoke on the bottom of the 450 shock is much longer. I think there is enough room to move the hole, though. Before I do that, I need to do further research on the linkage ratios of both bikes. I want to make it fit AND work like it does on the KLX450.

Other issues to be solved.... The subframe and seat do not clear the adjuster area of the shock, but the plastic does:







Modifying the sub and seat won't be too bad, but I did gain a lot of clearance in one area: under the shock reservoir where the pipe goes under.

250 shock:



450shock:



torch

[cutting torch]

Problems solved!

I made an angled cut out with the holesaw to clear the clicker:



I made a solid insert to fill the hole and welded it up. Also I drilled and milled the yoke where I needed it:



Here is how it clears now:



Next up is to make frame stops for the triples.

torch

[BDI]

the shock doesn't move enough to hit during travel? Looks good for sure.

[cutting torch]

the shock doesn't move enough to hit during travel? Looks good for sure.

It did at first (barely), but I massaged the notch a bit after that pic. At the closest point (shock bottomed) it has 1/16 clearance.

torch

[byron909]

what is that clutch cover?? neat project

[cutting torch]

what is that clutch cover?? neat project

That cover is a custom one that I made about 13-14 years ago. I made it on a brake lathe, since that is all I had access to. That is also why it has that small cover in the center. That covers the hole that the spindle had to pass through!

torch

[alward25]

Are you using the upper and lower KLX triple clamp too? Will the kx 500 wheel work too? I would love to upgrade my front suspension.  Great metal work you have going on too.

The forks will work. The head tube length is within the adjustment range of the triples, and both bikes use the same head bearings.

On the linkage ratio.... How is that determined? I would guess that it is wheel (axle) travel:shock travel.

I wonder whether that is a constant or progressive ratio, though.

Also, before I have even tried to fit the 450 shock, I have wondered if it is too long, and if a set of lowering links for the '92 would correct that and the ratio at the same time.......

I'm done wondering for now. If anyone has a smackdown for me, give it up! I'm not easily offended, and the smackdown will save me some time!

torch

[cutting torch]

I am using the triples as well, since the KLX forks are fatter.

I don't know if the K5 wheel will work or not. I got an '06 KX250F front wheel to use on mine. It's basicly the same as the KLX, but no odometer/speedometer stuff.

I'll make you a deal.....

If you go on kawasaki.com and research whether an '87 K5 front hub and rotor are the same as your year's hub and rotor, I will tear down and compare the parts I have to see if it works.

The difference is going to be in the axle diameter I'm sure, but that may not hurt you. The solution to that could be as simple as getting the right wheel bearings and spacers.

After all that, we might just need to compare measurements. We'll cross that bridge when we get to it, if needed.

Also, if you go that far, I think I have an '08 KLX450 front axle that I will sell you.

torch

[cutting torch]

The fork swap has been (mostly) completed!

Initially, I thought the triple clamp swap would be straight across from frame to frame, but I was wrong. The headset bearings are the same, and the head tubes were only different by 1/16. Well, race to race was a lot different, so I had to make a .200" spacer to go between the spanner nut and the bearing. I'll need to make a better one later, but this one worked for the mockup and fab of the stops.

You may be shocked by the following photo of how I made the spacer:



That was a plain old miter saw with a generic carbide contractor's blade. It cuts aluminum quite well. I cut aluminum on my tablesaw as well. I know, I'm nuts! As the pic shows, I did not cut all of the way through the bat to get the spacer I was looking to make. IF you decide to cut AL like this, and you are cutting off a small piece like my spacer, NEVER cut all the way through! If a blade tooth hooks it, it will fly like a bullet! Also, let the blade stop before you bring it back up through the cut.

This is the rough cut spacer:



And this is where it went:



torch