Have you considered changing the front sprocket to a either a 16 or 15 tooth and then retake the acceleration test. Remember the weight (mass) to gear ratio plus power band (rpm range) plays a role.
Yes, the top end speed will suffer when you change to a 15 tooth counter sprocket, however reaching the 60 mph mark will be a bit quicker.
Then as pointed out, the rider's ability wrt a quick reflex along with the ability to make a quick yet controlled pull away, plus the correctly timed gear changes is also key.