KDXRIDER.NET

I just completed my fork conversion on my kdx 220. This site was very helpful and I did somethings a little different. List of parts;
2001 kx 250 forks - $70
2001 kx 125 triple clamps - $20
1994 kx 125 wheel - $40
2001 kx 250 axle $9
Racetech gold valves - $97
RB-like stem spacer - $0 made it
Kdx stem swap - $0 habor freight press
Kdx stem machining to seat bearing removed .007" for 4mm -$0 did it carefully with file sandpaper
Stem bearings -$0 reused
Headlight mount brackets lower fork clamp -$0 made from formed .09" sheet metal
Tube height above upper triple - 0.625" top of tube per kx spec
Floated mid valve, stock shimming
Fork springs stock kx 250 per racetech recommendation - $0
Gold valve base shims;
10 - 24mm x .1mm
1 each .1mm tck, 16, 24, 22, 20, 18, 16, 15, 14, 13, 12, 11
2 .5mm base plates
Fork guards 2007 kx450 modified -$26
Fork guard brackets to pick up middle hole -$0 made it
Stock kdx brake line and caliper
Stock kdx fender
Bar mounts reversed
Devol solid bar clamp -$22

The stem mod and spacer do allow the forks to be raised higher while keeping kx20 tube height. Effectively lowers front end well.

I weigh 220lbs and consider myself a B rider. Im just east of pittsburgh pa and ride single track except a yearly trip to Croom riding park in Florida. Thats where the real draw back of the stock forks is apparent. Even though I resprung for my weight, removed shims, and changed fork oil levels I could still bottom the forks on the high speed sand whoops. But back in the technical single track of PA the forks were not that bad.

I will modify kdx axle to put odometer back on.
If you plan well and are not in a rush you can get very nice parts on ebay without a bunch of mismatched stuff you cant use.

I bought the bike for $1300. It had not been riden since 2008 and was bone stock including original tires chain and sprockets.

Other mods i did include fmf rev pipe, pro circuit silencr, RB carb mod, boyseen reeds, wiseco forged piston, RB head mod, and airbox mod.

I would like to add photos but dont know how too.

I hope this helps someone and shows you can do it without a lot of money if you use some ingenuity and make parts yourself.

Welcome to kdxrider.net. Good job!

Welcome to the forum and thank you for the info. I like that you did all that work yourself. I was Croom last weekend with my KX fork modded 220. Fortunately for myself (I guess) I'm not fast enough to be able to bottom out the forks on the sand whoops. Theyre such an improvement over the stockers for me. That plus the Shinko 90/100/21 front tire is great in the sand. My GoPro footage from there makes the sand whoops look like a smooth dirt road. I'm thinking hit the gas. When I'm actually there I'm thinking let off the gas!

Oh im sure i cant bottom the kx forks, but you can hit the whoops wide open and that bottoms the original forks.

Here are some photos;

Pic of bike


Head light sheet metal mounts to bottom of light. Made one for each side.


Since the kx450 center bolt didnt line up on 01 forks, I made a bracket that went from center bolt to outer bolt mount. Then drilled a hole where kx450 guard hole was and welded a nut on back. Some plastic cutting to clear. See black cap screw.



Next I mounted the cable clamp to the fork guard and cut off the old slider guide so that just the ring was left to protect fork from the guard when sliding.


I spaced the cable clamp with 1/4 inch spacers and cut clearance channel in fork guard for brake line.



The rb-like spacer sleeve installed. Note the aluminum bar stock I used was already 37mm and had a black ceramic coating on it.


Per kx250 manual set fork height at tube to .625, which is .71 to top of endcap


Hope this helps someone

Malibu406 wrote:Per kx250 manual set fork height at tube to .625, which is .71 to top of endcap

Did you shorten the forks internally?

No I did not. I want to get some rides on it before considering that.

Understanding the kx fork is an inch longer and reading through several post of others having incorrect front geometry after the swap, I decided to take some measurements. Note I am not debating the merits of internal lowering, just giving some measurements for thought.

Quick reminder, I machined the kdx stem to permit the lower bering to rest on the kx lower triple clamp. Some leave a gap, others fill the gap with a shim, but RB machines it. So that is what I did. Also, I made an exact sleeve spacer to RB's. Lastly, I installed my forks .625 to the end of the fork tube to the upper clamp per the kx250 manual. Also note, I never measured anything from the stock arrangement prior to doing mine. I figured RB had it all figured out and I did not recollect his modification requiring shortened forks.

Ok, sorry for long back story.

So tonight I reassembled the bottom kdx clamp to the kdx forks. The original marks on the tube were clearly visible. Note, my kdx forks were slide all the way DOWN with only about 1/8" of fork tube sticking out. I then measured from the center of the axle to the lower bearing seating surface and got 27-1/4".

Since the kx forks are an inch lnger, I expected to get 28-1/4" on my conversion. So I measured the conversion and got, guess what, 27-1/4". Exactly the same!

Ok, then that means the wheel must be too close to the fender for the fork travel. 2001 kx250 fork travel listed as 305mm = 12" So I measured from the fender to the knobby of the new tire as best I could and got 11.5 -11.7".

So while all of the maching and spacers + the .625" fork tube extension above the upper clamp per the kx250 manual gave me exactly the same geomtry, a big g-out (which I cant see me ever doing, on purpose any way) could allow the wheel to hit the fender. In theory to avoid this I would want to lower the forks .75" to give me .25" margin on g-out.

Then to restablish the 27-1/4" axle to lower tclamp bearing surface, I would lower the fork tubes .75" in the clamps But since thy only stick put 5/8" I couldn't do that because of the RB spacer I made? Hmmmm is it coincidence my geometry perfectly matched before and after? If i just lower my forks now and run 27-3/4" axle distance versus the original 27-1/4", would it matter much? I guess I will try both and see?

Your use of a spacerunder the top triple clamp is making the upper clamp rest higher on the tall KDX stem. That is keeping that distance from having to be taken up by raising the tubes even higher in the fork clamps.

What sag numbers are you running on the shock?

Yes I agree and thats what the spacer thickness was intended to do. With my spacer thickness and tubes at .625", the net is about an inch the forks are slid up. After work I wiill look up my sag numbers as I dont remember them off hand.

Why did you have to machine the KDX stem to get the bearing to fit? Did you use the KDX bearing?

The press length of the kdx stem is 3-4 mm longer and sticks out of kdx stem. So when you press the bearing on it stops before contacting the kx clamp effectively lowering the clamp by this amout. Many have simply done it this way, but i did not want the clamp lower. Plus i just think that is the more correct load path thru the shoulder versus id

If I may add... The KDX lower clamp is taller in height than the KX clamp. The "within the clamp area" portion is taller on a KDX stem than the KX stem.

It has been a while since I did this and wanted to follow up one one thing. In my post I mention my swap conversion measured 27-1/4” from bottom of lower triple to acle center and that was the same as the stock forks slid all the way down. My forks were from an 01 250. My friend bought an 01 kx125, so I measured it and got 27”. So I actually have 1/4” more clearance to bottoming than the kx. I have not had any negative issues to date.

So, maybe my geometry was always not the best with the stockers all the way down for my 225 ass. Remember I sprung the stockers for my weight, removed shims, changed preload and plated with oil heights and viscosity with only minor improvement. The conversion to the kx forks is better in most respects. However, for slow technical stuff or liesure riding, I think the stockers were better. Everything else the kx conversion is an improvement.

Thanks for the follow up and evaluation!

I have only been able to get a few rides on the conversion. The original forks were definitely better in the slow rocky stuff. The kx forks are better most everywhere else. The one problem I see is it can be a little sketchy going fast and hitting smaller rocks, especially when turning. Sometimes it just wants to skip out. Havent wrecked yet, but its coming if i dont fix it. It seems like midstroke harshness under fast fork action.

Was going to start with oil height adjustment. And yes the bladder system is still intact, though their removal seems to be what most have done.

Any suggestions?

Have you read about disabling the bladder?

When you said you floated the midvalve, I assume you got rid of the oring and put a spring?

How much float do you have?
Spring rate?
Oil weight?
Your weight I full riding gear?

Sorry for any typos, trying to use cell phone.

I have read some threads. They start to get confusing though as some take it further and start grinding for increased flow.

Technically i only replaced the oring with race tech spring and left shims alone.

Gold valve with stack shown in opening post.

Maxima 5wt at 90mm

235lbs with gear.

5/8” fork tube protrusion

Pivot works rebuild kit

Spring rate?

There is a white ring on the bladder that you can take off to disable them.

Why not just send the forks to a tuner to get them done? I understand wanting to do it yourself and all but sometimes it pays to just get them done by a professional.