I HAVE AN 250X MOTOR IN MY 250R, PEOPLE ALWAYS ASK ME HOW TO MAKE IT WORK.....WELL LISTEN UP, HERE IS AN EASY WAY TO DO ANY CONVERSION.....TAKE 4 POLLS, DRIVE THEM IN THE GROUND, TAKE A 1X4 OR SOMETHING AND MAKE RUNNERS FROM EACH POLE, AT THE TOP, LIKE A SQUARE...NOW TAKE SOME HEAVY DUTY STRING, AND TIE THE FRAME UP TO THE RUNNERS AT THE FOUR CORNERS, MAKER SURE IT IS LEVEL AND STRAIGHT, NOW TAKE THE MOTOR, PUT IT IN THE HANGING FRAME,AND TIE IT UP AT ALL THE MOTOR MOUNTS ON THE MOTOR....NOW CENTER AND LEVEL THE MOTOR OFF...NOW YOU CAN TAKE AN EXACT HANDS FREE MEASUREMENT OF THE MOTOR MOUNTS YOU WILL NEED TO FAB UP......THATS IT.

 

That sounds like a great method for creating motor mounts but I've always had a different question in the back of my head. If the motor you are installing is much larger (like a road bike motor), how do you rig up the chain and sprocket system. I would imagine that the rear sprocket location is changed to facilitate the mutation but am unsure. Also, the drive sprocket location in relation to the swingarm pivot location has got to be an issue. Binding and unwanted torque during swingarm travel is going to come up whenever such a different engine is installed. Your 250 two-stroke to 250 four-stroke is obviously much easier to deal with.