kx500 cylinder on kx250

[oldskoolkrome]

I have a liquid cooled KX250 that i want to go bigger with. I was curious if you could do like the honda guys and just put a 500 head on and basically get instant horsepower. I know i would need a bigger carb, maybe different reeds and possibly a different pipe (although i am currently running an fmf gold series and a turbine 2 silencer) what i want to know is what else would need to be cahnged over eg: cylinder head, crank, rod, ignition module, what to do with the powervalve, whether or not the cylinder would just slide in place or if i would need to adapt it to my motor. I think that the motor is a 1998 because t has the "electrofusion" plating. Any help would be greatly appreciated.
Thanks,
Ryna

 

[mtk]

The "Honda guys" put an entire CR500 engine into a CR/CRF frame.

No, it won't work.

 

[oldskoolkrome]

I guess my next question is what the differences between the 250 and 500 frames are. if i find a complete 500 could i hang it in my frame without any major hassles?

 

[Filthy_McNasty]

I guess my next question is what the differences between the 250 and 500 frames are. if i find a complete 500 could i hang it in my frame without any major hassles?

They are very different frames. But the swap can be done if you have a bit of fabrication talent, you wouldn't be the first to do it.

 

[oldskoolkrome]

Fabrication wont be a problem. Will my exhaust and ignition work with the 500 or will i have to replace that as well? does anyone have a complete motor that they want to get rid of?

 

[76GMC1500]

Neither the exhaust or the ignition will work. The engines run at very different rpm ranges which would throw out the pipe timing and ignition timing/rev limiters. Your silencer will still work with some fabbing, though.

 

[Filthy_McNasty]

The main challenges you are going to have is fabricating the engine and exhaust mounts, and sourcing a 500 exhaust that will work with the frame. You'll have to use the 500 ignition, carb, radiators, etc...

 

[Studboy]

I've seen a few KX250/500 hybrids around here. It seemed like everything fit well with some modifications.

 

[oldskoolkrome]

I seems like this might endo up costing more than what i anticipated. maybe i will just try to find a new 250 cylinder instead.