RB Designs retired? Any recommendations?

Questions and comments about converting to beefier forks..
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soup-n-sandwich
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RB Designs retired? Any recommendations?

Post by soup-n-sandwich »

Hi guys,
I'm looking to have 2006 KX450F front end married up to my 2002 KDX220. I have contacted Ron Black of RB Designs but so far no response. I understand there was talked about him retiring some time ago. If this is the case is there anyone else you would recommend that understands what actually needs to be done to properly fit the KX450 front end to the KDX?

I understand it's more than simply pressing the KDX220 steering stem into the KX450's lower fork clamp...right?

Thanks guys,
Chris
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bufftester
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Re: RB Designs retired? Any recommendations?

Post by bufftester »

RB has retired completely as I understand it. Fredette may be of some help.

You can use the KX upper and lowers if you can find bearings to convert. You just need an upper bearing with an OD of 47mm and width 12mm and the same ID as the KX stem. Same for the lower but with an OD of 55 and width 17mm. The harder part is matching the stem length, which can either be done by using the KDX stem, or making spacers for the KX one. If I'm not mistaken I think the KX stem is the same diameter as the KDX one as well, if so then you're just down to matching stem length or adapting it. Take some measurements between the 2 forks and see what you are dealing with.
soup-n-sandwich
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Re: RB Designs retired? Any recommendations?

Post by soup-n-sandwich »

Jeff Fredette doesn't touch the fork conversion at all. I just got off the phone with him.

On most of the fork conversion that the guys on here are doing will the stock KDX stem fit correctly into whatever top clamp they are using? I mean if they used a KX500 clamp assembly does the steering stem from the KDX fit snugly into the KX500 top clamp hole? My guess is, it does...but this isn't the case with the 2006 KX450F clamps.

I just noticed that the stem of the KX450 has a slightly larger stem hole than the OEM KDX. This means is I use the KDX stem with the KX450 clamps the top clamp will be flopping around on the KDX stem.

Does anyone have the conversion done already on their KDX? I would like to see how the spacer is used that Ron Black made. The spacer seems lit would be to take up the slack vertically in length. Is this correct?

It seems like I may be better off using the KX450 stem and find bearing to fit the KDX frame...no? I just don't see how the KDX stem is going to fit correctly into the top clamp of the KX450. This is the first time I'm digging into this mod so please forgive my ignorance on this.

Thanks guys
C
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Re: RB Designs retired? Any recommendations?

Post by bufftester »

Assuming the KX stem is the same length or longer than the KDX stem I would pursue looking for bearings first. With the KDX stem you would need to shim the top clamp hole (which has been done and is documented on this site), but bearings are way easier then you just have to worry about spacers for stem length. RBs design is a spacer/bushing that fits in the KX upper clamp to reduce the hole to that of the KDX stem, and the spacer part on top accounts for the difference in stem length. If the KX stem is shorter than the KDX stem then you're back to using the KDX stem and finding a shop that can press the stems in and out and machine the bearing seat area on the lower clamp. Take a long walk through the fork swap forum on here, there have been a lot of different styles done. And ask questions, we have a lot of smart fabricator dudes on here
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Re: RB Designs retired? Any recommendations?

Post by soup-n-sandwich »

bufftester wrote: 05:33 pm May 11 2023 Assuming the KX stem is the same length or longer than the KDX stem I would pursue looking for bearings first. With the KDX stem you would need to shim the top clamp hole (which has been done and is documented on this site), but bearings are way easier then you just have to worry about spacers for stem length. RBs design is a spacer/bushing that fits in the KX upper clamp to reduce the hole to that of the KDX stem, and the spacer part on top accounts for the difference in stem length. If the KX stem is shorter than the KDX stem then you're back to using the KDX stem and finding a shop that can press the stems in and out and machine the bearing seat area on the lower clamp. Take a long walk through the fork swap forum on here, there have been a lot of different styles done. And ask questions, we have a lot of smart fabricator dudes on here
Ok yes the KX450 stem is a tad longer if not the same length. It's hard to know exactly how long either is because they are still pressed into the lower clamps. It does appear that the upper bearing is the first issue and the second would be a simple spacer. Ahh yes I noticed that on RBs design I see that upper wider area of the spacer. So that part is the part that is the vertical spacer and the rest takes up the space in the upper clamp's mounting hold to accommodate the stem of the KDX. In this case I think my situation is a bit different because of my choice of "doner" parts from the 2006 KX450F.

I've attached the KX450 clamps and stem with the factory bottom bearing (seems to fit perfectly into the KDX lower race). The upper bearing is far too large but if I could find the right bearing and have a space made I might be okay.
I'll do what you said and spend some time looking over the existing post in the fork conversion section of the forum.
Thanks man!
Chris
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Re: RB Designs retired? Any recommendations?

Post by SS109 »

Simplest way is to swap the KDX stem in to the KX450 lower triple. Sometimes this requires knurling for a proper fit but not in all cases. He did two of mine, '90 KDX stem in to ''96 KX125 lower and '98 KDX stem in to '06 KX250F lower, and neither required knurling. Some people instead of using his spacer shimmed the stem and used large washers to fit the the upper triple clamp. It's not the perfect solution by any means but it has been done.

To fill the space between the KDX stem and KX OEM upper RB made a spacer to fill the diameter and the extra height. I can make these spacers. I also can do the stem pressing for the lower. If anyone is interested I will do it for the same cost as RB charged, $45 for the spacer plus shipping or the complete steering stem removal from the KDX lower and press, and knurl if necessary, the stem in to the KX lower along with the spacer at $145 plus shipping.
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Re: RB Designs retired? Any recommendations?

Post by soup-n-sandwich »

ahhh.. SS109. Yes I would like to send this stuff to you. With Ron Black out of the mix now I thought this was going to be a nightmare to find someone to do this for me. With all the talk about "KX" fork conversion I assumed that everybody was talking about the older 2 stroke bikes not the new KXF line of bikes. I learned that he 06-09 KX250F fork were 47mm Showa and used appropriate clamps. The same year(s) 450F had 48mm Kayaba with the appropriate clamp. I found this out the hard way. The length of the 450F stem seems very very close in length as the OEM KDX.

I thought the spacer that RB made was for the older KX two stroke bikes only...no? Have you got a chance to work with 2006-2008 KX450F clamps/stem?

So based on the pictures I posted here you still think that he better way to go is by using the KDX stem even though it appears that the KX450 stem will work IF and this is a big IF...if I can find the correct size upper bearing?
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Re: RB Designs retired? Any recommendations?

Post by bufftester »

SO the 200/220 and the 450F have the same lower bearing which is good news. The upper bearing for the 200/220 is 25X47X15, the upper for the 450F is 28X52X16. In theory you just need a 28X47X16 bearing, unfortunately they don't make one in that size that I know of which kind of puts you back in the KDX stem swap area.
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Re: RB Designs retired? Any recommendations?

Post by SS109 »

soup-n-sandwich wrote: 07:04 pm May 11 2023 ahhh.. SS109. Yes I would like to send this stuff to you. With Ron Black out of the mix now I thought this was going to be a nightmare to find someone to do this for me. With all the talk about "KX" fork conversion I assumed that everybody was talking about the older 2 stroke bikes not the new KXF line of bikes. I learned that he 06-09 KX250F fork were 47mm Showa and used appropriate clamps. The same year(s) 450F had 48mm Kayaba with the appropriate clamp. I found this out the hard way. The length of the 450F stem seems very very close in length as the OEM KDX.

I thought the spacer that RB made was for the older KX two stroke bikes only...no? Have you got a chance to work with 2006-2008 KX450F clamps/stem?

So based on the pictures I posted here you still think that he better way to go is by using the KDX stem even though it appears that the KX450 stem will work IF and this is a big IF...if I can find the correct size upper bearing?
All of the modern KX's from at least 1996 and up, both 2T and 4T, have a larger top bearing, and hence stem, and this is what the spacer was designed for. I have the spacer on my '06 KX250F front end and it fits perfectly and it was the same spacer on my '96 front end. To be up front, no, I have never played specifically with a KX450 front end conversion. However, I don't recall anything being special about the steering stem on them vs the KX250F. I know the '06 KX250F and 450F use the same steering head bearings so I would imagine the stem is most likely identical as a cost saving measure on Kawi's part.

Anyway, I can do it and mock it up on my '98 KDX just to make sure everything fits properly. Of course, steering stops would be your responsibility just like with RB.

If you want to do it I will need...
KDX lower triple with stem
KX lower triple
New lower bearing and seal. Preferably new upper bearing as well (I will pack new bearings with Bel-Ray waterproof grease for you as the lower is a pain to do once installed!)
The KDX upper washer and the two stem nuts
Oh, and please wipe off any excess grease and dirt but it doesn't have to be spotless. Cheapest way to ship is normally in a USPS flat rate box.
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Re: RB Designs retired? Any recommendations?

Post by soup-n-sandwich »

Hey man. Ok cool! I'll have to order the new bearings both upper and lower. So I'm just ordering the bearing for the KDX right? Stock OEM. I assume the bearing are all the same on models of the 200 and 220 from 1995 to 2006? Any particular brand you think would be best? All Balls, Tusk, Walmart?
I guess I'll need your information and payment method. I'll try PMing you.
Actually I don't see a way to PM you. I could try smoke signals but you're really far away from me. Any thoughts?
Also will I need to replace the bearing race in the frame when reinstalling the new bearing?
Thanks man,
Chris
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