Maintenance & Technical > KX500 Steel Frame Conversion (SFC)

K5 SF Frame Conversion. Where do I start?

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stupidmoto:
I know this question has been asked a million times, but which KX250 frame is the best/easiest frame to convert? I've been wandering around on here for about 2 weeks now and I really can't find a conclusive answer. I read that some people say that the 99-02's are the easiest to do, but why? Where do they differ for the 03, 04, and 05-07? There is a bunch of KX250 of all different years for sale around where I live, so thats not an issue. And what all is involved? I plan on making this a Dual Sport/trail/motocross bike but most of the time it will be in street legal Supermoto trim. But that brings up even more questions like jetting, lights, etc for running on the streets. Obviously it won't be a daily driver, it will be a weekend hoon machine. Any help?

motopunk:
the engine swap into the kx250 steelframes is always easier as in af-frames...

first you should find out, which year kx250-ergonomics you like the most ...   
1990-1993 you could always use the stock swingarm without changes
1994-2003 you have to choose between the 500 swingarm, older 250 swingarm with spacers because of the changed linkage-mounting on the frame or modify the actual 250 swingarm to the k5-engine
 in ī93 came the bigger swingarm-bolt and bigger bearings to the 250īs (on my bike i drilled the engine holes, to fit in my 93-frame ) the 500 always use the smaller bearings like the 250īs 92 and older . good way is to drill the swingarm to fit the 93 kx250-bearings-kit

1990-2002 you need to cut off the headstay and make a new front-headstay
2003-2008 have a back-headstay so i would prefer one of this bikes
 
the same things on all years are modify the front-motor-mount, modify an exhaust, and modifying the tank to fit to the bigger engine...

and here is my bike build..  http://der-motopunk.de.tl/projekt-kx500-.htm

don46:
The 99-02 is quite easy, I would not use the 500 swingarm, the concept of going to a newer frame we make the assumption that we can get a better feeling chassis as well as handling. the 250 swingarm is easy mod if you have the tools. I've done a couple of AL framed and 1 250f steel framed. for me I like the 250f framed 500 the best, it handles well, is quite narrow and just has a good feel to it. there are boatloads of blown up 250f steelies, nice thing about these, no tank mods, no headstay mods, you do have to mod the frame cradle.

stupidmoto:

--- Quote from: don46 on November 13, 2013, 09:54:03 AM ---The 99-02 is quite easy, I would not use the 500 swingarm, the concept of going to a newer frame we make the assumption that we can get a better feeling chassis as well as handling. the 250 swingarm is easy mod if you have the tools. I've done a couple of AL framed and 1 250f steel framed. for me I like the 250f framed 500 the best, it handles well, is quite narrow and just has a good feel to it. there are boatloads of blown up 250f steelies, nice thing about these, no tank mods, no headstay mods, you do have to mod the frame cradle.

--- End quote ---
Is the 99-02's any easier than the 03 and 04? What's the difference between the 99-02's and 03 and 04 modification wise? I know the headstay is in the back on the 03 and 04, but is everything else the same? What's the swingarm mod?
I do like the idea of a 250f steelie. The only problem is SF 250f's are hard to come by and expensive where I live for some reason. The cheapest one I can find is $2100! Thats pretty expensive for a donor bike IMO. I'll keep my eye out for a cheap one. But for the time being I think i'll stick with the idea of a KX250.

motopunk:
like i said:  first you should find out, which year kx250-ergonomics you like the most ... and then do it!  :wink:
i had listed all options , which are always there for conversion... 

the idea with the earlier steely kxf 250 or rmz 250 (same bike except the plastics) i s also good option.
 in my case i had a 250 frame laying around, looked at the market which model parts are available and bought all needed parts on ebay.

the k5 engine is easier to do in the 250-frames as i thought before i had the engine...  if you take an 94- 08 frame, you could also use the 250 radiators without modifying...
 the 4stroke-rads are diferent and it needs a little bit modifying to the k5 engine , but there is nothing, that couldnīt be made...  :-D

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