KDXRIDER.NET

I just picked up a 2000 KX125 with a blown engine for $400. I'm pretty excited about that. I'll be putting a KDX 200 or 220 motor in (still looking for the right donor bike).

This will be my second hybrid. My 1st (CR125 hybrid) can be found http://www.kdxrider.net/forums/viewtopi ... 11&t=10789:


I ride steep, tight, rocky, singletrack trails. i don't go over 40 mph most of the time, so top speed doesn't matter to me. Luggability and super slow speeds are what I'm looking for in this build.

I had a couple questions this go-around.

1) Is it possible to use KX125 carb (Keihin 36mm Air-Stryker) on this build?
The way I read the info, is the KDX PWK 33mm and 35mm carbs have the same outer dimensions. Then it sounds like the PWK 36mm and 38mm share the same dimensions too (which is larger than the kdx). Since I'm using the kx airbox, that won't be a problem. however, the reed cage boot is going to be too small on the kdx. Can I use the reed cage from the 125?


2) Is an E or H model preferred for the 2000 frame? (I don't want to debate which is better in general, just which will fit and work best with this frame). My research leads me to believe that it doesn't really matter since I don't have to cut the front headstay off like a newer kx.


3) are the Clarke or IMS tanks preferred for these builds?


4) any secrets to making the pipe fit without having to cut/dent it?

Thanks for the help.

1. Yes you can use the KX carb. I did on my latest hybrid. It is a real tight fit but it can fit in the KDX reed boot. The kx reeds and boot will not work.
2. Go with the H-model for several reasons. The primary being the rear headstay has to be cut off the either one and the H-series will still have the front headstay to use like the KX.
3. I haven't tried an oversize tank but I think you may find issues with the head to tank clearance. Right now I am putting a KX250F tank on mine so that I can update the look. Even the oversize f tank is no bigger than the stock KX125 tank.
4. My pipe fitting secret is to use an old set of fat handlebars as a bending lever. They fit tight in the small end of the pipe and won't deform the opening. Go in small increments. Even when you get it just right, the pipe will still be a tight fit and will want to rub on the downtube when you are putting it in place. A thick copper spacer in the head and a small bend/dent on the inside corner around the downtube will still likely be needed unless you want to extend the headpipe, which cause other issues. FYI, I have found that every pipe is a little different. A BIll's pipe had no chance to work. I had one FMF that had a little longer headpipe and was easier to make clear the downtube than another one I had.

Based on your riding description, I would recommend finding a 220 donor. Desert pipe and RB head and you will be happy.

Thanks Doctord23, you rock. That's just the info I needed. Do you feel that your kx125 carb is as good as a RB modded kdx200 carb? Or did you have Ron mod your KX carb too?

On my Hybrid I used the stock pipe, and I trimmed down the seam weld on the first bend, but it really wasn't an issue since I had a torque ring for a spacer. Other than moving the pipe mount brackets it was almost a straight bolt on affair. I used a KX250 Turbinecore II SA as well.

The H-models seem to fit a little better with fewer pipe issues on a 99-02 than the E motors, but plenty have been done of both.

Thanks bufftester, good to know.

One more question:

What about FMF Gnarly Torque vs Desert pipe? Does one fit better than the other, or is it a wash?

Also, are all FMF Gnarly pipes the same for both E and H motors? For instance, will an FMF gnarly torque be the same size for all E and H motors, or did they change through the years?

I currently have the kx carb on my 200 hybrid and an RB carb on my 220 hybrid.
I think the KX carb works good, but it is hard to compare the two. The 200 is pretty explosive up top and the 220 is good power everywhere. FYI, I had to remove the throttle position sensor on the KX carb because it hit the frame. I just capped it off. There are no electronics to connect it to anyway.
I also once tried the Mikuni TM38 off of a 2002 kx125 on my 220 and it was a low end beast, but lacked top end.

As for FMF pipes, the woods is definitely easier to fit because as you push the desert pipe farther away from the engine at the headpipe, it tends to want to hit the radiator and shroud of the kx. On the 200, use the woods. If a 220, use the desert. Or use a PC on either from what I hear. I haven't tried one.

Sweet, thanks for the info. I have my eye on a couple KDX220's this weekend. Hopefully I snag one soon to start the project. Thanks everyone.

I'm trying to determine if this is the stock piston or not. Can anyone verify? Since it doesn't have any numbers, I assume it's not a wiseco.

One more question, can you use a KDX rear brake on the KX?

With the "B" on the top of the piston I would say that it is a stock piston. Stock are sized A,B,C,D.

I have not tried to fit it but the KDX brake set up looks the same as the 2000 KX250 parts I have. The only difference I noticed besides the brake line is the reservoir is a different shape on them.

Cool, thanks for the info! A new wiseco will be put in tonight.

I reused the KDX brake on my Hybrid rear...Used the KX mounting plate, the KDX caliper, KDX hose, and KDX reservoir on the KX master cylinder/brake lever. The KDX lever wont work unless you swap over the mount from the KDX frame. The master cylinders are the same for both, I just used the KX one because I was too lazy to take the levers off and swap them over. Also like the KDX reservoir better because 1. its larger, 2. it has a bolt on cap (the KX is just a screw on). Had to trim my frame guards to fit the larger reservoir but that was easy. Also, if you use the KDX caliper on the KX bracket, the rear caliper guard (the white plastic one) won't fit. May end up going to the KX caliper for this reason since I ride some really rocky stuff that makes me think the guard might be of benefit. I also used the KDX front caliper, hose, master cylinder/perch on my hybrid and it fit like a glove.

great info bufftester, thanks. I'll hang onto those parts then.

Early 90's KX125 intakes bolt up.

What are you guys doing for kickstands? I'd rather avoid a swingarm kickstand if possible.