The 250r motor is outdated compared to modern 2 strokes, it would take about $1200 in motor work to make it comparable to a modern cr250 motor.
A big mod for 250r's is the CR ignition, the CR ignition is $400+ from what I remember.
250r is a AMAZING bike, excellent for many different build types and racing situations, it can be bored out to a saber cylinder or a puma cylinder if you want BIG HP. But thats strictly for drag racing, I wouldnt build a saber or puma for off road riding or racing it would just be wrong.
They are cool but need alot of money to hook up, I would buy a 250r if I were looking to restore and keep as a collectible item.
Im toying with the idea of doing that with a honda 350x or the quad version of the 250x, build it inside the house on the wall or hung from the ceiling in the garage piece by piece...lol
Anyway, a 250r as a collectable or as a hybrid for racing would be really cool.
400ex hybrid Finished!
http://www.youtube.com/watch?v=YMDIAw8UskQ