Just pull the dang clutch bell off already and there is a good chance your problem will be solved after you file down your shoes and put them back together. I am starting to think that during break in he didnt allow the tires to spin freely while getting on the throttle.
Did you happen to put it up against a wall during break in and pressed the throttle so it wouldnt go anywhere or did you hold down the buggy while giving it gas so that it wouldnt take off not allowing the wheels to turn?
Either that or the shoes were bad to begin with and had burs on them creating them to heat up and stick.