The radiator hanging underneath isn't the best place as it must creat a lot of drag,also it is trying to cool the engine using air off the exhaust dumping through.I guess lowering it lets some of the hot air bypass at the expense of more dragThese early machines weren't designed to be as fast as I he current incarnation.There was a YouTube video a few years back of a chap modifying his cowl to encourage the heat to exit away from the radiator,a but ugly but functional.