'04 KDX 200 to 04 KX 125 hybrid build

[B737driver]

And so it begins......Thanks in advance for answering questions that surely will arise.

Early in the game, this is what I've done so far...
1. I have the KX entirely disassembled down to the frame
2. The motor is out of the KDX.

Here are the bikes I'm starting with

[B737driver]

Hoping all this helps someone out down the road.


Step 1 is reaming the back of the KDX case to 17 mm in order to accept the KX swingarm bolt.

Step 2 measuring and re-measuring to assure the cut is right on the KX swingarm. Comparing the KX to the KDX this is what I'be found.....

The back of the KX motor, where the swingarm bolt goes through, is 76mm. The KDX is 94 mm. Difference of 18mm which is where others have come up with 9mm per side on the cut of the swingarm....got it.

The swingarm bushing is 54 mm and the current uncut swingarm is 58 mm. 4 less. OK so. ...

Taking 9mm off of each side on the swingarm results in a new measurement of 49mm. So taking 9mm off of the bushing would result in a measurement of 45mm.

I can't mock it up yet because I haven't cut out the KX motor mounts....just trying to figure it out mathematically.

Here is my first dilemma. ...I determined the midpoint of the KX and KDX swingarm bolt holder on the back of the case, for lack of a better term, and measured to the midpoint of the sprocket. I found that the KX is 81.5 mm and the KDX is 86mm. This would indicate that the motor needs to "slide" 4.5 mm to the right in order to have sprocket alignment. Am I missing something?

2nd dilemma .......considering pressing out the swingarm bearing before the cut to avoid getting aluminum on the bearing. Which way do they press out? Toward the middle or outwards?

[Tedh98]

2nd dilemma .......considering pressing out the swingarm bearing before the cut to avoid getting aluminum on the bearing. Which way do they press out? Toward the middle or outwards?

IIRC, they can go in/out in either direction. There isn't any type of lip that makes it a one way deal.

That KX looks super clean!

[kx200]

What brand of head light do you have
I use the stock head stay but you need to oval out one of the holes.
also use the air boot from the KX250 so the carb lines up
I also used a stock KX250 silencer but added a inch to the input

[KDXohio]

subscribed.

[Tedh98]

I also used a stock KX250 silencer but added a inch to the input

That is interesting, I used a 2004 KX250 silencer (same year as frame) and didn't have to modify a thing. It bolted on like it was meant for it.

[B737driver]

2nd dilemma .......considering pressing out the swingarm bearing before the cut to avoid getting aluminum on the bearing. Which way do they press out? Toward the middle or outwards?

IIRC, they can go in/out in either direction. There isn't any type of lip that makes it a one way deal.

That KX looks super clean!

Excellent thanks.

[B737driver]

What brand of head light do you have
I use the stock head stay but you need to oval out one of the holes.
also use the air boot from the KX250 so the carb lines up
I also used a stock KX250 silencer but added a inch to the input

The headlight is the KLX 450R style Chinese knock-off. Easy to find on ebay, and cheap. I like it, some think it's too "street fighter" style. I was just trying to update the look a bit.

So the kx 250 air boot lines up better, but did you still have to modify the boot to fit the KDX carb? My guess would be yes.

[B737driver]

Been cutting, grinding, sanding all day. Motor mounts are out and frame is pretty well cleaned up. Pics to come. Never cut or ground metal before and all in all it wasn't too bad. But I did stay at a Holiday Inn Express last night.

[kx200]

I am using a 36mm Lectron that has a 38mm input bell.
I also did not do anything with the front motor mount head stay.
I did remove some aluminum from the top of the stay so the bottom of the radiator hoses don't rub as bad.
My silencer was close to fitting but only about a 1/4 went into the pipe.
I also reused the stock front frame brackets.
When you mock them up for the welding use some thin washers between the motor and brackets.
That way the motor won't be so tight when you reinstall it.

[kx200]

next on the list is some graphics but I'm to busy racing

[KDXGarage]

WOW. Nice KX as well as the KDX.

[B737driver]

A few random shots....
1. Frame without motor mounts

2. Just had to put the motor in the frame......used the kdx swingarm bolt. Haven't reamed the motor yet. It fits.....

[B737driver]

Here's the KX just before I pulled the motor. Gotta sell that engine. Very low time. Wonder what I can get for it. ....
[youtube][/youtube]

For some reason I can't get the youtube thing to work....here's the link

[kx200]

I too need to do something with the 125 motor. Do you think they are worth $400?

[KDXGarage]

Just for curiosity (right now), what KX parts are left over on this? I have an '05 KX125 that I am keeping as a MX bike.

[KDXohio]

I too need to do something with the 125 motor. Do you think they are worth $400?

Good running motor id say at least 400

[B737driver]

Just for curiosity (right now), what KX parts are left over on this? I have an '05 KX125 that I am keeping as a MX bike.

I have the running motor and all associated components. Electrical, top and bottom end, carburetor, stock pipe (dent included), and the silencer. Think I'm using most of the other stuff. I've got all this for sale on C-List in Dallas for $800. Some interest by shifter cart guys, but no takers yet. This price seems in line with what guys on e-bay are selling for. May be a little high, but gotta start somewhere and this motor has very little time on it.

[B737driver]

Well, I talked to 2 machine shops today and neither was very interested in drilling out the case to 17mm. One reluctantly said they'd give it a shot using a hand drill if I would find a 17mm ream with a 15mm pilot. I remember seeing one somewhere, but now I can't find it. Looks like I may be taking it on myself. Think I'll just step it up slowly and try to keep it in line.

[Tedh98]

I bought this bit on eBay years ago and used it for the first time not long ago. Made the job really easy.

hybrid drill bit