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Having 2x F series and 1x worked E series I have done my fair share of trail blasting, albiet a few years ago.

I have never riden a H series but am sure it's a step forward both performance and reliability wise.
I believe there was no updates over the 10 years there were out???? (apart from bringing out a 220....)

So my plan is to buy a H series KDX as well as a '06+ AF KX250 or 450 for its rolling frame.

The KDX motor will be freshened up and the KX forks and shock will be revalved to suit my style of trail riding/enduro.

I'm sure there will be a bit of stuffing around fitting the motor to the frame. I am a boilermaker so can easily make up required brackets and can even cut and shut frames if needed (but obviously would rather not).

First question is, is it as easy a job as I am making it out to be?

Haven't found any threads where people have already tackled this. Know any 'how to' links?

Which AF frame KX would you go for?

Thanks in advance.

We do have a section which is dedicated to hybrid builds. You might dig through there and see what you can find. Motor mounts, head stays, and swingarm width / pivot bolt size are the biggest challenges. Obviously welding aluminum has it's own set of problems, but as long as you have the equipment to do it.....

The biggest challenge is removal and fabrication of the lower engine cradle portion of the frame.
Kawasaki 4 strokes have a single down tube while the 2-strokes have a double down tube with the exhaust exiting between.
It has been done and I believe that you can buy the frame replacement pieces to where you just need to cut out the old and weld in the new.
The other downside is that the 4-strokes have a smaller fuel tank.

Tank wise I think they offer oversize tanks for the 250f and 450f if that is ever a concern.

KDXohio wrote:http://www.kxriders.com/forums/index.ph ... 466.0.html

Yeah have seen the Service Honda KDX. Is awesome.

From this I now need to find someone who has done the mods required so I can see what difficulties that had. Can't seem to find anything.....

Crankn wrote:Can't seem to find anything.....

I don't think there are too many KDX/AF conversions. I think your best bet is to look at the other types of AF conversions to see what is involved. While those won't give you specifics for what you are wanting to do, I think it will be the next best thing.

I had a 03 CR125 that was fairly easy to do. I bought it already done. The only thing is that Aluminum frames will transmit a lot more engine vibration through to the rider. In the woods it is a little to stiff also. You will have to soften up your suspension. I made a new hybrid using a 04KX 125 chassis. It too is a easy conversion. The stock KDX fmf pipe fit with out cutting, that can be tough job.

Here is the link to an aluminum RMZ hybrid.
AF KXf would likely be similar.

http://www.kdxrider.net/forums/viewtopi ... uki#p92451

doctord23 wrote:Here is the link to an aluminum RMZ hybrid.
AF KXf would likely be similar.

http://www.kdxrider.net/forums/viewtopi ... uki#p92451

Cool. Wish it was a more current thread. It doesn't seem that the thread writter is around to answer questions. He said he didn't do the work himself anyway. The pics do help :)

kx200 wrote:I had a 03 CR125 that was fairly easy to do. I bought it already done. The only thing is that Aluminum frames will transmit a lot more engine vibration through to the rider. In the woods it is a little to stiff also. You will have to soften up your suspension. I made a new hybrid using a 04KX 125 chassis. It too is a easy conversion. The stock KDX fmf pipe fit with out cutting, that can be tough job.

So the 125 KX frames will easily accept the KDX engine? Wonder if it's the same with the KX250 2T frame?
So what did you need to do to fit the motor into you KX125 frame?

Crankn wrote:So the 125 KX frames will easily accept the KDX engine? Wonder if it's the same with the KX250 2T frame?
So what did you need to do to fit the motor into you KX125 frame?

If you visit the Hybrid section here, you will get all the info you need. But in a nutshell, putting a KDX in a steel framed KX is pretty simple.

You could use a 250 two stroke frame, but you will have a lot of room between the engine and lower frame cradles/downtubes. It will work, it just looks funny. I basically had a 250 frame modified and ready to go, but couldn't get over how goofy it looked.

He's wanting an aluminum frame was my understanding?

KDXohio wrote:He's wanting an aluminum frame was my understanding?

Right, but his last post was asking about 2 stroke frames.

Crankn wrote:So the 125 KX frames will easily accept the KDX engine? Wonder if it's the same with the KX250 2T frame?
So what did you need to do to fit the motor into you KX125 frame?

Ah yes must have skipped over that 1

Yeah enquiring about 2 stroke frames keeps my options open. Especially if it's really easy :)

My main thought of going with a 4 stroke frame is to keep things looking more modern with the better option of parts etc.

I am looking at a reasonably priced KDX that I might buy. Project could be kicking off quicker than i thought

Tedh98 wrote: You could use a 250 two stroke frame, but you will have a lot of room between the engine and lower frame cradles/downtubes. It will work, it just looks funny. I basically had a 250 frame modified and ready to go, but couldn't get over how goofy it looked.

So the 125 frame is smaller than the 250 2 stroke frame?

Crankn wrote:So the 125 frame is smaller than the 250 2 stroke frame?

The 250 engine is larger and needs the downtubes/cradles to extend out further compared to the 125. The KDX engine fits in the 125 nicely.

If you do use a kx 125 frame buy the same year kx250 air boot. The 125 has a case reed intake and that make the air boot sit a little low. The 250 has a intake closer to the KDX style.

kx200 wrote:If you do use a kx 125 frame buy the same year kx250 air boot. The 125 has a case reed intake and that make the air boot sit a little low. The 250 has a intake closer to the KDX style.

Cheers for that