Sounds like a crank barring to me under a load it will throw the vibration out but not under a load you will vibrate more he may be good for a little longer if he stays low in RPM but if he reeves it to the moon it will go out fast and destroy itself Quickly and be way more Expansive As for the CR250R If your cylinder and Crank is still good in it and you just clean it up and put in new piston will be cheap if the crank is Shot and the cylinder is Toast it could very well be $1600 and that is more than the bike is worth I would Pule the Cylinder off and look it over and clean it up and with what you see ( if it is Bad I would part out the Bike on Ebay or Bye a second one like it and use the best parts off it or get a rated out Bike With a good Motor )