2017 KX250F - 2004 KX250

[umberto]

I was working on getting 2017 plastic put on my 2004 KX250, which involved buying the subframe, tank, and plastic from eBay.  I recently sold a couple of my bikes, and have been wanting a newer bike for a while.  Unfortunately Kawasaki has basically said screw two-strokes, so we are at an impasse.  I figured putting new plastic on my old bike would be as close as I would get.  In the process of buying the subframe and tank, I noticed that the guy had all the other components of the bike as well.  He said to contact him directly if I needed anything else, so I called him and inquired about the frame, swingarm, triples, and linkage.  He offered me a deal I had a hard time refusing, so it looks like I am off on an aluminum frame project. I haven't had a new bike in 26 years, so I pretty excited about having the latest and greatest.  

I spoke with Fl_sharpshooter about his project, and felt pretty comfortable with the project until I got the frame out of the box yesterday.  It looks like Kawasaki changed some of the design of the frame.  The y in the frame is now part of a larger piece that extends up to the steering stem.  This obviously negates the ability to grind away the weld and remove the y for re-positioning.  I guess at this point I am going to have to cut the frame and add something inside (like the old y joints had the solid tab that went inside the frame) and outside the y (plate weled onto the frame?) to reinforce the joint.  Anyone have any thoughts on if I'm on the right track?  I only get one shot.  

[KXDINO]

sounds good umberto , you will succeed , but i think you should punch out half a dozen frames and sell the rest , i have a 01 250 engine looking for a home , and the 17 are great platform , and when it completed you could show the out of touch japs this is what you should bring out.

[FL_Sharpshooter]

I was working on getting 2017 plastic put on my 2004 KX250, which involved buying the subframe, tank, and plastic from eBay.  I recently sold a couple of my bikes, and have been wanting a newer bike for a while.  Unfortunately Kawasaki has basically said screw two-strokes, so we are at an impasse.  I figured putting new plastic on my old bike would be as close as I would get.  In the process of buying the subframe and tank, I noticed that the guy had all the other components of the bike as well.  He said to contact him directly if I needed anything else, so I called him and inquired about the frame, swingarm, triples, and linkage.  He offered me a deal I had a hard time refusing, so it looks like I am off on an aluminum frame project. I haven't had a new bike in 26 years, so I pretty excited about having the latest and greatest.  

I spoke with Fl_sharpshooter about his project, and felt pretty comfortable with the project until I got the frame out of the box yesterday.  It looks like Kawasaki changed some of the design of the frame.  The y in the frame is now part of a larger piece that extends up to the steering stem.  This obviously negates the ability to grind away the weld and remove the y for re-positioning.  I guess at this point I am going to have to cut the frame and add something inside (like the old y joints had the solid tab that went inside the frame) and outside the y (plate weled onto the frame?) to reinforce the joint.  Anyone have any thoughts on if I'm on the right track?  I only get one shot.  

Looks like you've got your hands full. Just try to take it 1 piece at a time, it can definitely get overwhelming. The y-piece looks really low on the newer frame. I would seriously consider looking for or making a total replacement y-piece, I can see the radiators are going to give you a fit too. Not sure how tall the 250 engine is, but looks like you're going to have to extend the cradle too.

[umberto]

Thank you for the votes of confidence.  I have been having multiple "what have I done?" moments the last few days.  Earlier I was thinking about Sandblaster's AF project that used the cradle from a 2001 CR 250 two stroke.  I think that may make the most sense, as it will give me the higher Y piece with the rails already attached.  That way I just have to worry about trimming and adjusting as necessary.  I think the picture angle is misleading, as there is more room in the frame than it looks like.  I think the 250 should fit just fine.  If I was going to do a 500 that would be a deluxe wrestling match.

I'm going to use the two stroke radiators if possible, so the mounts will need to be redone on the bottom anyway. I think that would be easier than trying to put the much larger four stroke radiators back on.

I grew up working on hot rods with my dad, so I'm used to making stuff that isn't supposed to go together work.  I guess I need to just remember this advice:




   

[umberto]

I measured the frame from the swingarm bolt straight forward, and it was almost exactly the same measurement as my 04. I think I'll be good on space.

[umberto]

I made a couple of purchases for the conversion.  I bought a 2001 CR 250 frame so I can recreate how Sandlbaster and Jason did their 2007 conversion.  I paid $69 plus shipping for it.



I also found this later model KXF shock for the clevis so I can use my Stillwell re-valved shock.  It's pretty blown up, so I only paid $29 plus shipping for it.  It's hard to find just the clevis, so I was pleased to find this shock so cheaply.



Everything comes in next week, so I should be able to get started making some progress soon.  Just about the time it gets stupid hot in Oklahoma.  

[umberto]

I ran into a little snag with the frames. The KXF frame has a slight taper after the straight section, while the CR frame is straight with no taper. The KXF frame starts at a 4 1/8" gap.



And increase to approximately 4 1/2" right before entering under the foot pegs:



Not too drastic, but still a concern. Luckily I managed to enlist an ally. My son and I took the welding class I took when I built Goliath, and my instructor agreed to help me with it.  He's been working with aluminum for years, and didn't seemed fazed by the project at all. I get my frame on Monday, so things should start moving here pretty quickly.

[FL_Sharpshooter]

I ran into a little snag with the frames. The KXF frame has a slight taper after the straight section, while the CR frame is straight with no taper. The KXF frame starts at a 4 1/8" gap.



And increase to approximately 4 1/2" right before entering under the foot pegs:



Not too drastic, but still a concern. Luckily I managed to enlist an ally. My son and I took the welding class I took when I built Goliath, and my instructor agreed to help me with it.  He's been working with aluminum for years, and didn't seemed fazed by the project at all. I get my frame on Monday, so things should start moving here pretty quickly.

This should be interesting. I did notice that four stroke engines are usually less wide at the bottom, hence the taper. Almost every 2 stroke has straight rails.

[umberto]

Looks like Photobucket declared war on me.  They will allow me to host pictures for the low, low price of $399 per year.   

[sandblaster]

You can post pics at KXguru.com and then link them here...

[sandblaster]

Or, if your a facebook freak go to KX Guru Racing and post the pics there, and then link them here  

https://www.facebook.com/groups/179257569231617/

[umberto]

Danger is going to let me park my pictures on his site, I just need to get with him on how to do it. In the meantime, my CR frame came in and it brought some good news. It also has a taper in it, and ends up at almost the same width as the KXF at the back mounts. I'm hoping it will line up without much modification. I'll post some pics when I get that all figured out.

[DP3601]

Ive havent been on in awhile and just saw this!  Wow you took a major turn from fitting the newer plastic to this...  I look forward to seeing how this thing turns out.  Im sure its gonna be one sweet bike when you get done.   

 

[umberto]

I get this from my dad: I'm a constant tinkerer.  I've been thinking about thinning the herd and buying a new bike, but I just can't drink the orange Kool Aide.  Doing this conversion gets me a new bike and the green two stroke I want.  Of course I wouldn't be doing this if Kawasaki would sell me the bike that I (and most of us) want in the first place.

[umberto]

I got the cradle section liberated from the CR frame yesterday finally.  My son is a competitive swimmer so I've been traveling to swim meets all over the Midwest this summer and haven't had much time for the garage.  August is pretty full as well, so it looks like progress will have to wait a bit.  On a good note, the cradle lines up almost exactly to the frame and won't require much modification.