One of the "many" reasons the motor runs hot is piston design. The piston is round and causes a lot of additional fricton. Cam ground pistons are wider between the front & rear skirt, and narrower from side to side. Take .004" off the piston on each side below the wrist pin hole to the bottom of the piston. Vintage Whizzer pistons are not round and run much cooler.
BTW........I have reduced my personal collection to only 11 Whizzers and several EZM proto-types. Of the 11 Whizzers, one will pull wheelies, another has 2 motors, 5 are vintage, 6 are New Edition, and one is a rare 2007 Ambassador "1" electric start.
Have fun,