it takes alot more than a bore, porting and all the bolt on parts available to gain 40mph over the stock 80-90mph on a banshee.
chances are it's just bored .40 over, with no porting, but i do see pipes, like he states...it's just too fast for him, but he didn't gain 40mph.
maybe over the 50 mph. badly worn engine before the new bore/piston ?