Looking to do KX Rear swap on 87 KDX200C

ClintNewkirk · Post by **ClintNewkirk** » 08:30 pm Jun 17 2016

I am new to the site and I recently have picked up a 1987 KDX 200 to make a fun vintage ride. I have seen people doing the KX125/250 rear end swap on these and I'm curious as to are these bolt up or is there some serious modification work needed?

Thanks for any help guys!

Post by **KDXGarage** » 04:29 am Jun 18 2016

Are they putting a 1986 or so rear end on the KDX?? I can't say I have ever heard of the rear end swap or why one would want to do so.

I could see a disc brake rear change, like switching to 1989 - 1994 KDX200 rear wheel and brake setup. That could work with a few homemade tabs welded on and swingarm machining on the caliper hanger.

A 3 mm washer is also needed on the rear axle, as best I remember.

ClintNewkirk · Post by **ClintNewkirk** » 06:59 pm Jun 18 2016

Jason wrote:Are they putting a 1986 or so rear end on the KDX?? I can't say I have ever heard of the rear end swap or why one would want to do so.

I could see a disc brake rear change, like switching to 1989 - 1994 KDX200 rear wheel and brake setup. That could work with a few homemade tabs welded on and swingarm machining on the caliper hanger.

A 3 mm washer is also needed on the rear axle, as best I remember.

From the things I'm reading, it's a swap to a 88 KX250 swingarm/suspension, which they include the rear brake and wheel. The guys are saying it's better braking and a better controlling bike after the swap. The reason for the post, I'm hoping to find someone who's done the swap and would be willing to discuss it with me to see how much fab work, if any, is needed. From reading you'd think it's bolt and go, but I'm doubting.

Dekon · Post by **Dekon** » 08:22 pm Jun 18 2016

Can't really help you but I don't think it'll be bolt and go. You will at least need to fabricate a bracket to hold the rear master cylinder.

ClintNewkirk · Post by **ClintNewkirk** » 11:51 pm Jun 18 2016

Dekon wrote:Can't really help you but I don't think it'll be bolt and go. You will at least need to fabricate a bracket to hold the rear master cylinder.

Good call. I guess no matter which swingarm is used, if I go to a disc brake, I will have to fab that. Looks like I'll hit the local bike yard and see if I can find any goodies.

ClintNewkirk · Post by **ClintNewkirk** » 11:57 pm Jun 18 2016

Jason wrote:Are they putting a 1986 or so rear end on the KDX?? I can't say I have ever heard of the rear end swap or why one would want to do so.

I could see a disc brake rear change, like switching to 1989 - 1994 KDX200 rear wheel and brake setup. That could work with a few homemade tabs welded on and swingarm machining on the caliper hanger.

A 3 mm washer is also needed on the rear axle, as best I remember.

Thanks for the Info Jason. Any knowledge I can gain is a plus. This is my first KDX and I'm wanting to make a fun little GP (local southern ohio series) ripper. I hope to add photo's as I start the process. I picked the bike up on trade for an old Iphone 5 that I no longer used. Seems to be tons of info on this site and I'm sure you guys can steer me in the right direction when I get to a hard spot.

sarrant · Post by **sarrant** » 12:38 am Jun 19 2016

I'd really like to see this. just out of curiosity.

I mean, an '88 KX has a typical modern linkage setup (pro-link style). A C Series Kdx has a a pushrod style with the linkage at top of the shock. The original Uni-trak pushrod style shock mounts in a different orientation and doesn't even have an upper shock mount point on the frame, nor is there a place for the linkage below the swinngarm. It just seems like it would require a fair amount of frame modification to execute.

bob_jones · Post by **bob_jones** » 08:41 pm Jun 19 2016

Just FYI I'm about to try the disc brake swap with with e-series kdx parts. I have all my parts I'll probably get a chance to start putting it together this week. My bike is an '86. I got a bunch of measurements and it looks like everything should come real close to fitting. Not swapping swingarm / suspension. There would be fab work for that and I just don't see any real benefit in that. Could likely throw geometry out of whack and there is really not much wrong with the design of the rear suspension anyway. Front is different story.

hbgod · Post by **hbgod** » 09:18 pm Jun 19 2016

I have an 86 kx125 and an 86 kdx200. The swingarms are totally different. I dont see how they would mount up at all. i thought of it because of the rear disk. You can however to a rear wheel swap and have a caliper bracket welded to the swingarm.

bob_jones · Post by **bob_jones** » 10:51 pm Jun 19 2016

I have yet to confirm but it looks like the caliper holder slides onto the same sticking out slider thing that the brake shoe carrier did. I'm going out on a limb here but there is a good chance it will be easy. Meaning the e-series kdx. I don't have any kx parts and the fiche looks different

Dekon · Post by **Dekon** » 11:39 am Jun 20 2016

Here is a link to a rear disc conversion someone did on this site. It's not a KX rear end conversion but has a rear disc set-up on it. Maybe you can get some ideas from this build.

http://www.kdxrider.net/forums/viewtopi ... 19&t=12349

bob_jones · Post by **bob_jones** » 01:58 pm Jul 04 2016

Update: I swapped the rear wheel assembly from a 1990 kdx200 onto my 1986 kdx200. The E wheel, hub, sprocket, caliper holder, and disc is direct fit onto C axle. I used the E spacer on the left, the C spacer on the right, the C shim on the right, and a big washer on the right. I had to grind the thing that sticks out of the swingarm (I'll call it the "key") to fit the E caliper holder. The key is far too big to fit the slot on the holder. It was grind-fit grind-fit grind-fit... there was not a lot of material left on the key when i got done. It seems to work but If I had it to do again, I wouldn't use the E holder. I would use a holder with a bigger slot like a KX or possibly a ninja. I also had to swap the Allen head bolts that hold the caliper for hex head that are a little longer because the allen bolt heads hit the swingarm. I also hadon't to do a lititle grinding on the swingarm to clearence for the front caliper bolt. I had to use small spacers from Lowe's between the caliper holder and the caliper because the caliper sat too far right to grab the disc. The spacers made a perfect fit
I used the E brake line, master cylinder, reservior, pedal, and adjuster bolt. I used the C spring. I had to weld one perch on the frame similar to the one that is already there that holds the top of the original cover over the pedal pivot.
I then had to make a bracket from scratch to hold the master cylinder. Mounting the master cylinder was the hardest part for me fitting and measuring and grinding and cutting and re-fitting and all of that.
So now I have rear disc. They are not real "grabby" but they will lock the rear wheel at speed. I probably need to bleed some more hut also the pads and disc could be worn out. The brakes don't squeak at all. Spent a while riding and seems to be a good setup so far.

The point is, it worked. So there it is.

Post by **KDXGarage** » 02:46 pm Jul 04 2016

Congratulations on getting it done!

BillyWillicker · Post by **BillyWillicker** » 04:37 pm Jul 05 2016

I'm pretty sure the '85 KX250 rear swap is the one spoken of. My '87 KDX200 came to me with a KX250 rear shock and link on it. The KX link is adjustable and the KX shock is a 46mm shock with an 16mm shaft where the KDX shock is a 40mm shock with a 14mm shaft.

Post by **KDXGarage** » 02:58 am Jul 06 2016

Is the shock not longer??

BillyWillicker · Post by **BillyWillicker** » 02:40 pm Jul 06 2016

I seem to remember it being longer as well Jason. Was a good fit however.

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