2002 kx250 swap

[Kawifiddy]

Hey guys i bought a 1991 kdx200 for 50 bucks in rough shape but the motor fires up, I have a guy wanting to sell a 2002 kx250 roller for 175, how much work am I looking at to put the 200 in the 250 frame

[sandblaster]

I'm sure someone has done it but typically guys put the 200's into the KX125 chassis 
You could break down that 250 chassis and sell the parts.
Then buy a 125 chassis and go for it.
But either way, the 200 with some effort can go into either chassis.

[umberto]

I just sold a 2003 KX 250 with a 2001 KDX 220 engine. The 250 frame allows you more room, but it complicates the exhaust as compared to the 125. I would recommend selling the 250 and finding a 125 if you can. The other thing to consider is that year KDX engine has an issue with breaking KIPS valves, and they aren't made any more and are very hard to find in one piece. It might make more sense to flip that one and look for a 1997 and up engine.

If you want to keep going, you will need to trim the swingarm and bearing races. Also, you will need to do something with the pipe. That year KDX is not a perimeter framed bike, which means you can’t use the KDX pipe in the KX frame. You may be able to use a later model pipe, but I’m not sure the flange is the same. The motor mounts will not line up, so you will need to modify them.

The end result is a really nice woods bike. I just think it might be easier to start with different models.

[SS109]

A KX125 would be an easier place to start but the 250 will work and has been done. First, I suggest visiting the "Hybrid" subforum over at KDXrider.net and reading up on the various swaps that have been done. Nothing wrong with using the E-series ('89-'94) engine as BDK makes steel replacement KIPS valves now. They don't shred like the OEM aluminum ones. However, some engine parts are no longer available so be aware.

[umberto]

That's interesting that BDK is building those for KDXs, and at around $130 they are a whale of a deal.  They mentioned that they would build other models if the interest is there.  Maybe it's time to start a KX250 and a KX500 campaign.