Here is an ingenious method from: http://datsunzgarage.com/engine/index.htm Remove the dome and main piston from each carb so you can look down the tip of both fuel nozzles. Screw each mixture nut exactly 10 turns down from fully up. Each full turn drops the nozzle tip 1 mm, so 10 turns puts the tip of the fuel nozzle 10 mm (1cm) down....which happens to be the 23mm float bowl level. Then look down the tip of each fuel nozzle and adjust each float to set the gas level at the fuel nozzle tip.