The OKO 30mil doesn't have a "normal" drain plug where you can use the clear hose up beside the float bowl trick. It only has a nipple down there for an overflow stand tube.
You set the float height dry with the float bowl off and the carburetor turned on a 45° angle so that the float tang is pressing against the needle but NOT compressing the spring built into the float needle. The "float height" is the difference between the LOWEST part of the float and the mating surface with the carburetor in ^^^^ that configuration.