Are the carbs from a 1000? Do the tops of the carbs have a 3/8 inch raised portion or are they relativly flat? One air cutoff valve - 1000 . Four air cuttoff valves - 1100. Flat tops are 1100 carbs. They should be parallel to the body and 15.5 mm when the rack is up on end and the floats just touch the valves. Hope this helps.