New to the forum so heres my first question for all you experts. As I recall, a 1973 cb750 was fitted as standard with 28mm carbs. When I measure mine there 30.5mm at the head side of the throat. Am I measuring the wrong place or have they been changed or modified. They look standard but I think every other part of the motor has been played with which is making me wonder. Any advice will be greatly appreciated.