im guessing you cant do it, as when you put in or take out a motor out/in the frame you have to take the rocker box's off to get it to fit, then when the motor drops into place in the frame you put the box's back on.
if the box's are off you might be able to take the top, front and bottom mounts off then loosen the rear ones so the motor swivels , then you might get it up to clear the frame. might have to take the gas tank off to????? depends how low it sits on the frame. its a stock bike?