Hybrid Questions KDX250 RM125 Possibilities

[hlewis]

I've been thinking about this for a while now and it has know come to more of a reality and I'm thinking that it could actually happen.

I have a 94 KDX250 that I absolutely love to ride except for the size weight of it. I had the opportunity to ride an 04 KDX200 the other day and was amazed at the difference in size. I also recently purchased an 01 RM 125 that is not currently running for fairly cheap. I bought it from a co worker thinking that I would fix it and then sale it.

So I was in my garage last night and I've always thought it but never really talked about it. But does anyone know or have any idea if that 250 motor would fit in the RM frame?

It looks like it might have a chance of squeezing in there but I'm a little hesitant to just dive in and in the end it not work. I of course would rather try and put it in a KX250 frame but I don't have one. So I know it's been talked about before and I'm not aware of anyone actually doing it. I know most will say just go for it or say get a 250 frame but does anyone have any experience in this area?

Just for fun here are a couple of pics of both bikes.

[img::]https://lh4.googleusercontent.com/-iwDf ... 084419.jpg[/img]


[img::]https://lh4.googleusercontent.com/-aOIK ... 084508.jpg[/img]

[img::]https://lh3.googleusercontent.com/-g_8U ... 084642.jpg[/img]

[img::]https://lh3.googleusercontent.com/-Ul-7 ... 084858.jpg[/img]

[Tedh98]

I don't have any concrete information to give you, but can share my thoughts.

I'm fairly certain that the downtubes on the RM frame will need to be modified. I'm basing this on a an '04 KX250 and '04 KX125 frames that I have. Everything between the two frames are identical except the downtubes. The 250 frame has the downtubes pushed outward to make room for the larger engine.

I've seen other hybrid builds where people have cut and put in new downtubes, so it is definitely doable.

[hlewis]

Yeah even looking at the pictures it almost looks like the engine cradle of the 250 frame is a little larger. The 250 frame almost looks flat directly under the motor where the 125 looks to angle up towards the downtube more. I don't really want to change out the downtube, so that alone may kill the idea. I need to get a few rough measurements of the cradle's of both bikes. I checked the swingarm width's and it's not exact but it is definitely doable.

[Tedh98]

I'm guessing a quick measurement from the swingarm pivot to front of engine of both bikes will give a general idea of how far off things are.

[Julien D]

If I had to guess, you'd be cutting out the entire engine cradle and fabricating a new one.

Just a guess, of course.

[SS109]

I agree with juliend and ted that you are probably going to need to cut and fabricate a new cradle. The KDX250 engine is quite a bit larger that the 200.

[hlewis]

I had a chance to look at a CR250 today and you can definitely tell the difference in the cradle between the 125 and the 250. The cr had an almost flat like shape to it directly underneath the motor more like that of the KDX250.


Maybe I'll let this one pass on the idea of the hybrid and keep looking for the perfect KX250 roller. I actually saw a 2003 KX250 roller listed on the local craiglist a few months back for $300. Which would have been a steal and of course I missed it. I'm sure it probably sold within a day or two of being listed.

In the mean time I'll keep chugging along on the 250 tank.

[Julien D]

I bet you could shoehorn a kdx200/220 in there pretty easy :). Always wanted to see that done...

[SS109]

I bet you could shoehorn a kdx200/220 in there pretty easy :). Always wanted to see that done...

No doubt. Just do the smaller 200/220 hybrid and ride it!

[Julien D]

Love the way the rm's handle. with a trail motor it'd be sick XD

[hlewis]

Well sold the 250 and bought a 99 200 and still have the rm. So I'm not sure where this will lead.

[KarlP]

I think I'd get the RM running and rideable. Work out any suspension/handling issues on the RM and then see if you feel like it would benefit from a different motor.