KDX hybrid build......

[HRDROKN]

Hey Guys...

I just wanted to share with you all my 99' KX125 / 03' KDX220 build. This build is in progress and comments are welcome!

I had picked up a fairly clean 2003 KDX 220R a few months back for $900. I had been riding this bike comparing it to my 300exc... if there is such a thing. There are a few things I like about the KDX and many things I like about the KTM! The KDX is easy to ride... the KTM can be a handful and I feel it the next day, but she handles so much better at speed. So rather than my original plan of a KX fork conversion etc. I picked up a 99' KX125 for the best of both worlds? Of course that is only what I have read...

:cool:

 

[HRDROKN]

Started stripping down the KX chassis early this morning and noticed that my lower motor mounts are of the double variety? Thought I read that that was different in the 99' compared to the 00'-02' frames. Not a big deal by any means... wonder if it was a change that some of the later production frames received in that year?

Also ordered up a 18" wheel and spokes to mate up with the KX hub.

I think I will take the forks and shock up to Dicks Racing for a rebuild/re-valve, since they are local.

 

[HRDROKN]

As of this morning the KX motor is out....

:cool:

 

[HRDROKN]

And now the KDX.....

:coocoo:

 

[HRDROKN]

After getting a first hand look at whats needed, I see that the actual cut on the swing arm is the least critical of the operation... you can do this with a hacksaw and file!

Did all the measurments and 9mm on each side is sufficient....

:whoa:

 

[HRDROKN]

The greatest concern and area to get correct is the swing arm bushing. It has to be fairly darn close, as it will set the overall compressed length.

Drilled the cases by 64ths to 21/32's then used a 17mm ream to finish....

:nod:

 

[HRDROKN]

Figured out a good way to hold the bushings while cutting.... I used the swingarm bolt in the vise!

I then used a flapper wheel to clean the cut, then hit the bushings on a carborundum disc and then a course stone to the target dimension.

:cool:

 

[99220sr]

Great Info, keep it coming.

 

[HRDROKN]

With all the swingarm mods out of the way, it was time to see how she was going to line up in the chassis...

And would the lower mounts line up..... it was close! So I will cut the lowers out and fab new ones....

;)

 

[HRDROKN]

Interesting...

Ive been playing with motor location as it compares to the pipe, airbox and fuel tank.... looks like things fit better the more you rotate the motor forward.

The boot on the airbox is too long and it seems as though the KDX boot would be a better fit....

With forward rotation, the pipe just misses the down tube.... a little dent in the pipe should provide desired clearance...

When you rotate the moto forward you lose the lower mount position...

And I have a solution....

 

[HRDROKN]

Needed to remove the rear headstay to fit the tank in place.... this is how we do it old school!

I will clean it up before I send it off to RB... along with the carb.

:nod:

 

[HRDROKN]

With the motor rotated further forward as the goal... I put the swingarm, wheel and chain on.... moved the motor around and I can't really tell much difference in regards to pressure on the chain guide, at least no more/no less than taking a tooth off the front sprocket

So I guess I will keep the motor rotated forward and work on some new lower mounts...

;)

 

[HRDROKN]

After trying several different ways of configuring the airbox, I think the best solution is to use the stock KDX box... it requires one of two modifications to fit correctly.

First and the best solution is to cut the stock KX airbox mounting tabs off and re-weld them to match up with the KDX mounts. You can see it in the pics. EDIT: This is not the best way to go as those tabs are used for the fender also! So the second way is the best!

Second, modify the stock KDX box and utilize the KX airbox mounts on the sub frame as is... I went this route as I'm not set up to weld aluminum. After cutting the KDX box for clearance I will fab some aluminum plate to cover the holes and provide for mounting.

;)

 

[HRDROKN]

Finished off the KDX airbox mount.....

;)

 

[HRDROKN]

I set it up with shock in place before taking all the suspension to Dick's. Hard to see from this pic, but there is at least .125" all the way around.

Here is the fender without the bolts in.... but they line up and the KX fender fits the contour of the box perfectly!

;)

 

[HRDROKN]

Got after the lower mount tonight, so this is what I came up with...

And welded...

;)

 

[HRDROKN]

Finished up with the front mount...

Pipe is sitting all the way in the head and looks like a small dent in the pipe to clear the downtube..... Hmmmm, just thinking that I don't have the exhaust gasket in there yet and that should give me some more clearance? Bottom line with the motor rotated further forward there is no need for a headpipe extension.

;)

 

[99220sr]

Great info, I know of a 220 motor for sale, I may buy it and keep an eye out for a kx.

Which year kx is best suited? Can the KDX tank fit in the KX frame?

 

[Joburble]

HRDROKN, you are an absolute legend! Great pics, great ideas. Thanks for all the info. :cool:

 

[whenfoxforks-ruled]

How did the head stays get back on? Vintage Bob

 

[ellandoh]

rear head stays are still gone?? pics in post 11 show front and rear stays.

 

[craig_enid]

Post #16 shows the rear are gone....

 

[whenfoxforks-ruled]

The front stay is still on. What in the heck, stays front and back? I would like to see the look on your face when you ride this bike. Nice job. Vintage Bob

 

[HRDROKN]

HRDROKN, you are an absolute legend! Great pics, great ideas. Thanks for all the info. :cool:

Thanks for the comps!

:nod:

 

[HRDROKN]

Ya, the 220 motors at least had front and rear head stays and the rear needed to be removed for tank clearance.

Picked up my suspension from Dick's Racing yesterday....

:cool: