Turn the carbs upside down so that floats are facing up. You need to measure from the seating surface where the float bowl will touch to the highest point on the top of the two floats. I had trouble measuring/holding, etc. so I made me a little jig out of 1/4" plexiglass. It was shaped like a "U" with the legs touching the the base of the carbs and the top cut to the correct float height.