Picked up a used set of 31 mm to go a big bore motor I was building. Decided to put them on my very nice blk/blk F 2. I noticed the "mounting rails that traverse the top and bottom of the carbs each have a bunch of simple factory marks on them. for example # 2 carb has only two marks . # 4 has about 8. Anybody know if they are "actual" marks that are ment for line up? or is it something else. Any help would be gratefully received. Sorry no pics, dead battery in camera..